Quote Originally Posted by Lee L
I think I saw someone else mention this earlier in the thread, but couldn't find it. At these magnifications you'll want to use a focusing rail. One driven by a rack and pinion or a threaded rod (like the Bogen 3419 Micro Positioning Plate) is best.

You can't focus effectively with bellows or by shifting the tripod at the magnifications you're talking about, so you need to move the whole rig (camera, lens, bellows) back and forth in very small increments to focus. It can be done with a sliding rail, but a rack & pinion or screw drive is much better.

Sorry to add to your equipment list. Have you considered reversing rings for stacking a couple of your existing lenses? See Shaw for how to do this and to calculate reproduction ratios.
Lee, I am aware of the difficulties of working at high magnifications and already use a focussing rack. I also use couplers and stacked lenses but I am looking at these movie lenses to go beyond what can be done with coupling.