100-400 MK II tripod foot WARNING

I just read this on the Fredmiranda forum and thought I'd share...

This guy may have over tightened, but perhaps/maybe not.

http://www.fredmiranda.com/forum/topic/1357309

Im about to order this lens and I think I'll replace the foot with the RRS ARCA foot.

dgumshu wrote:

I just read this on the Fredmiranda forum and thought I'd share...

This guy may have over tightened, but perhaps/maybe not.

http://www.fredmiranda.com/forum/topic/1357309

Im about to order this lens and I think I'll replace the foot with the RRS ARCA foot.

Kirk Photo has a replacement foot for US$80 - and is has a double-dovetail.

http://www.dpreview.com/forums/post/55484305

If you look at the piece where the screw goes into it's distorted looks to me like he over tighten the screw.

DBCossini wrote:

If you look at the piece where the screw goes into it's distorted looks to me like he over tighten the screw.

Seems that way to me too. It looks from the photo as if the insert is drilled and tapped all the way through unless the end broke off and is still in the hole.

If the insert is drilled and tapped through, it would be VERY easy to "jack" the insert out by over tightening the screw in the way he describes if the screw was long enough to reach the bottom of the blind hole in the foot. It would go straight through the bush and press down into the blind hole forcing the insert out.

What's disappointing is that Canon could easily have made the insert a 3/8" UNC adapter which a) would be impossible to jack out no matter how hard the screw was tightened and b) removable for use with a 3/8" tripod head or plate or whatever.

The three options for him now are to

a) replace the stock foot

b) ask a workshop to see if the hole can be tapped for 3/8" x 16 UNC (provided that the hole is not much bigger than 8.0mm which is the tapping drill size). He can then use a standard adapter like this.

c) just buy an after market foot from Kirk or RRS.

I just bought one of these lenses myself and I'll be using a Kirk replacement foot for it as soon as it (the foot) arrives and would advise anyone else to do the same before any accident occurs. At the very least, care should be taken to ensure that any 1/4 screw is NOT long enough to "bottom out" and thus jack the insert out.

This is only of passing interest but just for fun, I removed the base plate on the tripod collar where the tripod foot is mounted for a close look under a magnifier.

The small, black base plate appears to be die-cast alloy and is held in place with 4 x M2 (2mm dia) screws - two of which had a light application of Loctite or equivalent - on their threads. The base carries the M5 mounting hole into which the stock foot (or after market alternative) is bolted.

The M5 thread is implemented using a "helicoil" type insert (similar to the ones in the photo below) rather than a solid threaded insert like the 1/4" x 20 UNC one in the foot itself. In my experience in engineering, the helicoil type insert is commonly used for repairing damaged threads.

I'm guessing that Canon chose this method of implementing the thread because of the strength advantage over simply drilling and tapping the alloy base plate itself. However, I don't really see much strength advantage in this method compared with say, a solid stainless threaded insert (threaded on both sides) screwed into the base plate. Possibly, it's cheaper.

All this is academic I know, but what it boils down to is that you have the tripod foot bolted into this small, alloy base plate on the collar with a M5 screw. The foot is then bolted to something else (Arca-Swiss plate, ball-head or whatever) via a 1/4" x 20 UNC screw which screws into the bush which, as has already been established, is only an interference (push) fit in the alloy foot.

You then have the entire weight of the lens and camera body (which might in some cases also have a battery grip, flash, additional filters etc attached) ALL SUPPORTED BY JUST 4, TINY M2 WATCH SCREWS! Attaching any form of after-market foot makes no difference.

Obviously, there's no problem if the entire load is resting vertically downwards on the foot with the camera/lens rotated solely by means of the collar. However, I hate to imagine the shear stress on those 4 screws if the camera/lens were tilted into portrait mode using a ball head with the foot in the horizontal position. Or worse, with the whole rig hanging off the end of a tripod swung over a shoulder as some shooters do when moving around.

The Mk I version had a VERY solid collar and tripod foot cast as a single component that was built like a tank and impossible to break even if bounced around over the shoulder fixed to a tripod. The MK II is flimsy in the extreme by comparison and has nothing like the load bearing ability of the Mk I.

It seems to me the collar/foot design on the Mk II is seriously compromised in terms of load bearing capability especially given that this lens is even heavier than the Mk I. This is the only criticism I would make of the build quality of this lens and I fail to see why Canon wouldn't have made the collar/foot much beefier like the Mk I. Cost savings again, perhaps.

I'd recommend all owners of this lens to bear this in mind and avoid unduly stressing those 4 tiny screws when mounting the camera/lens on a tripod or carrying it around. At least, never carry it around hanging off the end of a tripod without some additional support. Also, when using any form of after market foot, make sure that the M5 screw used to mount it is NOT so long that it "bottoms out". If this happens and the screw is continually tightened, it could "jack up" the alloy base plate stripping the M2 threaded holes in the collar with potentially disastrous results. The sound of a heavy camera and lens hitting concrete must be one of the most sickening sounds it's possible to encounter!

Thanks for reading.

Thanks for the strip down.sacentre wrote:

You then have the entire weight of the lens and camera body (which might in some cases also have a battery grip, flash, additional filters etc attached) ALL SUPPORTED BY JUST 4, TINY M2 WATCH SCREWS! Attaching any form of after-market foot makes no difference.

Thanks for the strip down.

I do not see this as a weak point. And I can hardly imagine how this will be a point of failure in any normal use scenario

First of all the four screws are easily strong enough to not "break" or get "pulled out" no matter how much you swing the lens around while shooting.

In addition the four screws are well protected by the plate insert from movement stress (which otherwise could be a serious problem over time).

To me it seems Canon used these screws because they are short and therefore made sure that the fitting design supported using a small screw size.

Now I do not have your advantage of having the parts in front of me. But this is my take away from your pictures and explanation.

maiaibing wrote:

Thanks for the strip down.sacentre wrote:

You then have the entire weight of the lens and camera body (which might in some cases also have a battery grip, flash, additional filters etc attached) ALL SUPPORTED BY JUST 4, TINY M2 WATCH SCREWS! Attaching any form of after-market foot makes no difference.

Thanks for the strip down.

I do not see this as a weak point. And I can hardly imagine how this will be a point of failure in any normal use scenario

Depends one's definition of "normal" of course but you are right if we mean what normal care with no undue abuse usually implies. The design is unquestionably much flimsier than the Mk I  but hopefully adequate for careful folks. A wildlife shooter, say, carrying the camera and lens on a tripod over a shoulder and stumbling over rough ground could put undue stress on the joint.

First of all the four screws are easily strong enough to not "break" or get "pulled out" no matter how much you swing the lens around while shooting.

I wouldn't like to bet on that. "No matter how much" leaves a lot of room for abuse. My main point was in cases where a tripod is being used there is considerably less scope for swinging around or whatever than the much tougher Mk I.

In addition the four screws are well protected by the plate insert from movement stress (which otherwise could be a serious problem over time).

Yes, as long as they stay tight. I think the guy who had the disaster with the bush coming adrift reported finding one or two of those screws loose. Can't see how that happened with a new lens but clearly this was a case where his definition of "normal" is outside what you or I might accept.

To me it seems Canon used these screws because they are short and therefore made sure that the fitting design supported using a small screw size.

Now I do not have your advantage of having the parts in front of me. But this is my take away from your pictures and explanation.

Thanks for your valid comments.

I've just had this image by way of a promotional email from Kirk enterprises (I assume other Kirk LP-61 customers will have seen this too).

It appears that Kirk feel that some additional support for the weight of the lens is called for when used with their LP-61 plate and by extension, any similar product.

As I argued in my earlier post, these after-market plates, being considerably longer than the stock foot, allows the fulcrum point (if that's the word I'm looking for) to be much further forward along the foot (towards the front of the lens) which could have the potential to overstress the rear pair of M2 screws in the tiny black base plate on which the entire assembly hangs.

Perhaps Kirk have listened to and agreed to some extent with these concerns and have developed a product as an opportunity to attract repeat sales from customers who share the concern.  At the same time (and I'm being a bit cynical here) avoid any possible damages claims that might arise from damage to the tripod collar or worse, a lens falling off altogether when used with the LP-61 alone.  I wouldn't be surprised to see some type of disclaimer printed on the LP-61 packaging soon.

I continue to feel that Canon for reasons best known to themselves, have delivered a very fragile design in the way the foot is attached to the collar.They should have given us a similar, immensely robust arrangement to that of the Mark I and other long, heavy lenses in their line up.

Just my ten cents.

sacentre wrote:

I've just had this image by way of a promotional email from Kirk enterprises (I assume other Kirk LP-61 customers will have seen this too).

It appears that Kirk feel that some additional support for the weight of the lens is called for when used with their LP-61 plate and by extension, any similar product.

As I argued in my earlier post, these after-market plates, being considerably longer than the stock foot, allows the fulcrum point (if that's the word I'm looking for) to be much further forward along the foot (towards the front of the lens) which could have the potential to overstress the rear pair of M2 screws in the tiny black base plate on which the entire assembly hangs.

Perhaps Kirk have listened to and agreed to some extent with these concerns and have developed a product as an opportunity to attract repeat sales from customers who share the concern. At the same time (and I'm being a bit cynical here) avoid any possible damages claims that might arise from damage to the tripod collar or worse, a lens falling off altogether when used with the LP-61 alone. I wouldn't be surprised to see some type of disclaimer printed on the LP-61 packaging soon.

I continue to feel that Canon for reasons best known to themselves, have delivered a very fragile design in the way the foot is attached to the collar.They should have given us a similar, immensely robust arrangement to that of the Mark I and other long, heavy lenses in their line up.

Just my ten cents.

This product doesn't appear to be intended to deal with any perceived weakness in the foot assembly, but rather to support the front of the lens when the collar is loosened to rotate the lens. Here's a quote from Kirk's web page:

"The new Kirk quick release lens support for Canon EF 100-400mm f4.5-5.6 IS USM II lens used in conjunction with the LP-61 supports the front of the lens. By using the LS-1 lens support, the shift up and down is totally reduced when loosening the lens collar to rotate the lens. The LS-1 must be used with the Kirk's LP-61 which is sold separately."

I think it remains to be seen whether the foot assembly is as deficient as you seem to think. By placing a slot for a lanyard at the front of the foot, Canon is effectively inviting us to carry the lens (and camera) by the lens foot. I would be very surprised if Canon had not done the necessary testing to ensure it was safe to do so.

bhollis wrote:

sacentre wrote:

I've just had this image by way of a promotional email from Kirk enterprises (I assume other Kirk LP-61 customers will have seen this too).

It appears that Kirk feel that some additional support for the weight of the lens is called for when used with their LP-61 plate and by extension, any similar product.

As I argued in my earlier post, these after-market plates, being considerably longer than the stock foot, allows the fulcrum point (if that's the word I'm looking for) to be much further forward along the foot (towards the front of the lens) which could have the potential to overstress the rear pair of M2 screws in the tiny black base plate on which the entire assembly hangs.

Perhaps Kirk have listened to and agreed to some extent with these concerns and have developed a product as an opportunity to attract repeat sales from customers who share the concern. At the same time (and I'm being a bit cynical here) avoid any possible damages claims that might arise from damage to the tripod collar or worse, a lens falling off altogether when used with the LP-61 alone. I wouldn't be surprised to see some type of disclaimer printed on the LP-61 packaging soon.

I continue to feel that Canon for reasons best known to themselves, have delivered a very fragile design in the way the foot is attached to the collar.They should have given us a similar, immensely robust arrangement to that of the Mark I and other long, heavy lenses in their line up.

Just my ten cents.

This product doesn't appear to be intended to deal with any perceived weakness in the foot assembly, but rather to support the front of the lens when the collar is loosened to rotate the lens.

Here's a quote from Kirk's web page:

"The new Kirk quick release lens support for Canon EF 100-400mm f4.5-5.6 IS USM II lens used in conjunction with the LP-61 supports the front of the lens. By using the LS-1 lens support, the shift up and down is totally reduced when loosening the lens collar to rotate the lens. The LS-1 must be used with the Kirk's LP-61 which is sold separately."

I think it remains to be seen whether the foot assembly is as deficient as you seem to think. By placing a slot for a lanyard strap at the front of the foot, Canon is effectively inviting us to carry the lens (and camera) by the lens foot. I would be very surprised if Canon had not done the necessary testing to ensure it was safe to do so.

Fair enough. As you rightly say, it's early days and so far we've only heard of one failure of the foot itself - not the mounting point.

I agree about the strap. However, my comments are mainly concerned with the use of after market plates like the Kirk LP-61 rather than the stock foot. If any damage were to happen with an after market foot fitted - whether used with a strap or no, I doubt Canon would accept any responsibility for warranty repairs.

In the quote, Kirk are saying the purpose of the support is to "reduce" the lens shifting up or down while rotating.  We're not shooting while rotating so why would anyone need to worry about at bit of lens movement while changing from portrait to landscape?

Then they go on to say the support "must be used" with the LP-61 which sounds a bit like a warning to me ie don't use the LP-61 on its own.

sacentre wrote:

bhollis wrote:

sacentre wrote:

I've just had this image by way of a promotional email from Kirk enterprises (I assume other Kirk LP-61 customers will have seen this too).

It appears that Kirk feel that some additional support for the weight of the lens is called for when used with their LP-61 plate and by extension, any similar product.

As I argued in my earlier post, these after-market plates, being considerably longer than the stock foot, allows the fulcrum point (if that's the word I'm looking for) to be much further forward along the foot (towards the front of the lens) which could have the potential to overstress the rear pair of M2 screws in the tiny black base plate on which the entire assembly hangs.

Perhaps Kirk have listened to and agreed to some extent with these concerns and have developed a product as an opportunity to attract repeat sales from customers who share the concern. At the same time (and I'm being a bit cynical here) avoid any possible damages claims that might arise from damage to the tripod collar or worse, a lens falling off altogether when used with the LP-61 alone. I wouldn't be surprised to see some type of disclaimer printed on the LP-61 packaging soon.

I continue to feel that Canon for reasons best known to themselves, have delivered a very fragile design in the way the foot is attached to the collar.They should have given us a similar, immensely robust arrangement to that of the Mark I and other long, heavy lenses in their line up.

Just my ten cents.

This product doesn't appear to be intended to deal with any perceived weakness in the foot assembly, but rather to support the front of the lens when the collar is loosened to rotate the lens.

Here's a quote from Kirk's web page:

"The new Kirk quick release lens support for Canon EF 100-400mm f4.5-5.6 IS USM II lens used in conjunction with the LP-61 supports the front of the lens. By using the LS-1 lens support, the shift up and down is totally reduced when loosening the lens collar to rotate the lens. The LS-1 must be used with the Kirk's LP-61 which is sold separately."

I think it remains to be seen whether the foot assembly is as deficient as you seem to think. By placing a slot for a lanyard strap at the front of the foot, Canon is effectively inviting us to carry the lens (and camera) by the lens foot. I would be very surprised if Canon had not done the necessary testing to ensure it was safe to do so.

Fair enough. As you rightly say, it's early days and so far we've only heard of one failure of the foot itself - not the mounting point.

I agree about the strap. However, my comments are mainly concerned with the use of after market plates like the Kirk LP-61 rather than the stock foot. If any damage were to happen with an after market foot fitted - whether used with a strap or no, I doubt Canon would accept any responsibility for warranty repairs.

In the quote, Kirk are saying the purpose of the support is to "reduce" the lens shifting up or down while rotating. We're not shooting while rotating so why would anyone need to worry about at bit of lens movement while changing from portrait to landscape?

Sounds like just a matter of convenience.  I've got the Kirk foot, but don't plan to buy this.

Then they go on to say the support "must be used" with the LP-61 which sounds a bit like a warning to me ie don't use the LP-61 on its own.

I think they're just saying that the support is only compatible with (and therefore can only be used with) the Kirk foot.

I think you're reading more into this than is there.

This is only of passing interest but just for fun, I removed the base plate on the tripod collar where the tripod foot is mounted for a close look under a magnifier.

The small, black base plate appears to be die-cast alloy and is held in place with 4 x M2 (2mm dia) screws - two of which had a light application of Loctite or equivalent - on their threads. The base carries the M5 mounting hole into which the stock foot (or after market alternative) is bolted.

The M5 thread is implemented using a "helicoil" type insert (similar to the ones in the photo below) rather than a solid threaded insert like the 1/4" x 20 UNC one in the foot itself. In my experience in engineering, the helicoil type insert is commonly used for repairing damaged threads.

I'm guessing that Canon chose this method of implementing the thread because of the strength advantage over simply drilling and tapping the alloy base plate itself. However, I don't really see much strength advantage in this method compared with say, a solid stainless threaded insert (threaded on both sides) screwed into the base plate. Possibly, it's cheaper.

All this is academic I know, but what it boils down to is that you have the tripod foot bolted into this small, alloy base plate on the collar with a M5 screw. The foot is then bolted to something else (Arca-Swiss plate, ball-head or whatever) via a 1/4" x 20 UNC screw which screws into the bush which, as has already been established, is only an interference (push) fit in the alloy foot.

You then have the entire weight of the lens and camera body (which might in some cases also have a battery grip, flash, additional filters etc attached) ALL SUPPORTED BY JUST 4, TINY M2 WATCH SCREWS! Attaching any form of after-market foot makes no difference.

Obviously, there's no problem if the entire load is resting vertically downwards on the foot with the camera/lens rotated solely by means of the collar. However, I hate to imagine the shear stress on those 4 screws if the camera/lens were tilted into portrait mode using a ball head with the foot in the horizontal position. Or worse, with the whole rig hanging off the end of a tripod swung over a shoulder as some shooters do when moving around.

The Mk I version had a VERY solid collar and tripod foot cast as a single component that was built like a tank and impossible to break even if bounced around over the shoulder fixed to a tripod. The MK II is flimsy in the extreme by comparison and has nothing like the load bearing ability of the Mk I.

It seems to me the collar/foot design on the Mk II is seriously compromised in terms of load bearing capability especially given that this lens is even heavier than the Mk I. This is the only criticism I would make of the build quality of this lens and I fail to see why Canon wouldn't have made the collar/foot much beefier like the Mk I. Cost savings again, perhaps.

I'd recommend all owners of this lens to bear this in mind and avoid unduly stressing those 4 tiny screws when mounting the camera/lens on a tripod or carrying it around. At least, never carry it around hanging off the end of a tripod without some additional support. Also, when using any form of after market foot, make sure that the M5 screw used to mount it is NOT so long that it "bottoms out". If this happens and the screw is continually tightened, it could "jack up" the alloy base plate stripping the M2 threaded holes in the collar with potentially disastrous results. The sound of a heavy camera and lens hitting concrete must be one of the most sickening sounds it's possible to encounter!

Thanks for reading.

The breaking strength of a single m2 screw is around 300lbs... I think 4 of them can safely hold the lens. I suppose if you attempt to fight off a brick wall by swinging the lens from the end of a tripod as hard as you can you might be able to break one of the screws of you are very unlucky. Of course the lens itself will be dust by then, but at least you'll have shown how "weak" the tripod collar is.
--
-Adam
https://www.flickr.com/photos/90719248@N04/

sacentre wrote:

As I argued in my earlier post, these after-market plates, being considerably longer than the stock foot, allows the fulcrum point (if that's the word I'm looking for) to be much further forward along the foot (towards the front of the lens) which could have the potential to overstress the rear pair of M2 screws in the tiny black base plate on which the entire assembly hangs.

I don't see how the length of the plate affects the stress on the screws.  The weight of the lens on the 4 screws remains the same, regardless.

dherzstein wrote:

sacentre wrote:

As I argued in my earlier post, these after-market plates, being considerably longer than the stock foot, allows the fulcrum point (if that's the word I'm looking for) to be much further forward along the foot (towards the front of the lens) which could have the potential to overstress the rear pair of M2 screws in the tiny black base plate on which the entire assembly hangs.

I don't see how the length of the plate affects the stress on the screws. The weight of the lens on the 4 screws remains the same, regardless.

I'm not necessarily buying that there is a problem with the lens foot from Canon or that there's a problem with their foot or any other at all.

I will comment that a longer lens foot actually makes a longer lever depending where the load is stressed at.  It's called mechanical leverage, something I have first knowledge and experience with as an auto mechanic.  Commonly called a cheater bar, it's used to gain more leverage or mechanical advantage.  Basically a longer lever.  It works, trust me.

Steve Balcombe wrote:

sacentre wrote:

As I argued in my earlier post, these after-market plates, being considerably longer than the stock foot, allows the fulcrum point (if that's the word I'm looking for) to be much further forward along the foot (towards the front of the lens) which could have the potential to overstress the rear pair of M2 screws in the tiny black base plate on which the entire assembly hangs.

No it doesn't!!! The stress on the screws is totally unaffected by this. I thought you said in another post that you had some sort of engineering experience????

For goodness sake people. The guy who posted the scaremongering pics on FM self-consciously admitted "I am open to the possibility that this issue may have been exacerbated by an error on my part", and it is obvious from the damage to the insert that there has been some sort of abuse.

As for the gadget sold by Kirk to "support" the lens at the front, what a load of BS. The collar is only about 3-4 cm behind the point of balance. I suppose some mugs will buy it, but you would have to be pretty paranoid to believe it was necessary.

As the guy who posted the "scare-mongering" pics, I feel compelled to say that I was not trying to monger any scare. I was just sharing my experience for the benefit of the community.

I may have been an idiot for over-tightening the screw. Or I may have been an idiot for using too long a screw. Or the insert may have failed for other reasons, including a manufacturing defect/weakness (and my state of idiocy remaining undetermined). The state of the insert itself is not indicative of what caused the failure: you are seeing damage to it after it got detached from the head and needed to be extracted by pliers. There are 4 pages of information in that linked thread, including one very detailed analysis, with photographs, of the entire situation. I learned a *LOT* from that thread, not only about may or may not have happened in my case, but also general principles of machining and design, as well as how that tripod foot/collar was built. If you take the time and patience to read the whole thread, you might, as well.

So, feel free to make fun of me for what happened to me. Feel free to place the blame on me for the equipment failure. But you are doing me injustice when you ascribe fear-mongering as my motivation: I have zero interest in scaring you or anyone else. You take good photographs. I hope some day your manners catch up.

dherzstein wrote:

sacentre wrote:

As I argued in my earlier post, these after-market plates, being considerably longer than the stock foot, allows the fulcrum point (if that's the word I'm looking for) to be much further forward along the foot (towards the front of the lens) which could have the potential to overstress the rear pair of M2 screws in the tiny black base plate on which the entire assembly hangs.

I don't see how the length of the plate affects the stress on the screws. The weight of the lens on the 4 screws remains the same, regardless.

Landscapeforwouldn't landscape for funly of passing interest but just for fun, I removed the base plate on the tripod collar where the tripod foot is mounted for a close look under a magnifier.

The small, black base plate appears to be die-cast alloy and is held in place with 4 x M2 (2mm dia) screws - two of which had a light application of Loctite or equivalent - on their threads. The base carries the M5 mounting hole into which the stock foot (or after market alternative) is bolted.

The M5 thread is implemented using a "helicoil" type insert (similar to the ones in the photo below) rather than a solid threaded insert like the 1/4" x 20 UNC one in the foot itself. In my experience in engineering, the helicoil type insert is commonly used for repairing damaged threads.

I'm guessing that Canon chose this method of implementing the thread because of the strength advantage over simply drilling and tapping the alloy base plate itself. However, I don't really see much strength advantage in this method compared with say, a solid stainless threaded insert (threaded on both sides) screwed into the base plate. Possibly, it's cheaper.

All this is academic I know, but what it boils down to is that you have the tripod foot bolted into this small, alloy base plate on the collar with a M5 screw. The foot is then bolted to something else (Arca-Swiss plate, ball-head or whatever) via a 1/4" x 20 UNC screw which screws into the bush which, as has already been established, is only an interference (push) fit in the alloy foot.

You then have the entire weight of the lens and camera body (which might in some cases also have a battery grip, flash, additional filters etc attached) ALL SUPPORTED BY JUST 4, TINY M2 WATCH SCREWS! Attaching any form of after-market foot makes no difference.

Obviously, there's no problem if the entire load is resting vertically downwards on the foot with the camera/lens rotated solely by means of the collar. However, I hate to imagine the shear stress on those 4 screws if the camera/lens were tilted into portrait mode using a ball head with the foot in the horizontal position. Or worse, with the whole rig hanging off the end of a tripod swung over a shoulder as some shooters do when moving around.

The Mk I version had a VERY solid collar and tripod foot cast as a single component that was built like a tank and impossible to break even if bounced around over the shoulder fixed to a tripod. The MK II is flimsy in the extreme by comparison and has nothing like the load bearing ability of the Mk I.

It seems to me the collar/foot design on the Mk II is seriously compromised in terms of load bearing capability especially given that this lens is even heavier than the Mk I. This is the only criticism I would make of the build quality of this lens and I fail to see why Canon wouldn't have made the collar/foot much beefier like the Mk I. Cost savings again, perhaps.

I'd recommend all owners of this lens to bear this in mind and avoid unduly stressing those 4 tiny screws when mounting the camera/lens on a tripod or carrying it around. At least, never carry it around hanging off the end of a tripod without some additional support. Also, when using any form of after market foot, make sure that the M5 screw used to mount it is NOT so long that it "bottoms out". If this happens and the screw is continually tightened, it could "jack up" the alloy base plate stripping the M2 threaded holes in the collar with potentially disastrous results. The sound of a heavy camera and lens hitting concrete must be one of the most sickening sounds it's possible to encounter!

Thanks for reading.

The breaking strength of a single m2 screw is around 300lbs... I think 4 of them can safely hold the lens. I suppose if you attempt to fight off a brick wall by swinging the lens from the end of a tripod as hard as you can you might be able to break one of the screws of you are very unlucky. Of course the lens itself will be dust by then, but at least you'll have shown how "weak" the tripod collar is.
-Adam
https://www.flickr.com/photos/90719248@N04/

Correct. It wouldn't be the screw that would fail or snap just from tension.  If anything, it would be the thread in the soft alloy that would strip if the foot were stressed enough.