THX723

http://www.ebay.com/itm/NEW-Gold-Flash-FireWire-800-FW800-CF-UDMA-Compact-Flash-Card-Reader-IEEE-1394-/230758761847? Firewire CF card reader has been a dying breed, so it was a bit of a surprise...

You might look into Magic Lantern: http://www.magiclantern.fm/It supports the 5D2 and has Intervalometer with bulb ramping. It is in fact a firmware hack, so use at your own discretion, however...

I have been looking for the same myself. Indeed Hoya does make the x400 in 82mm, but in very limited production. The only reputable vendor I'm aware of is Digital Camera Gear...

You might consider the M-plate from Custom SLR:http://www.customslr.com/products/m-plate-pro#.UK2FNeQ818EPlate supports both Arca and Manfrotto clamps. Has a non-interfering mounting point for your...