macro focusing rail

Well I also have a stackshot, and use it extensively. It is perfectly usable in the field with the battery that cognysis also sells for exactly this reason. It is also perfectly usable with mp-e 65. Zoom in, make a run, put together in zerene stacker, done. It's a bit extravogant if you're just after a slider though, and remember this is a 1 axis device. For what it's worth, I also use a velbon slider, works for me. It's not the cheapest option but also not the most expensive. I've made stacks with it (moving it 1 'ridge' at a time, the controls for movement have ridges on them) but nowadays I just use this for rough positioning then use stackshot for the actual run. Have a look at  http://www.flickr.com/photos/jingleslenobel/sets/72157623492127788/ about half are with stackshot, half just handheld.