The AC-345 / AC-216 will definitely be bigger that's for sure! Actually the longer bellows wouldn't have been a bad choice for me either with hindsight as I think that the AC-254 is pretty extended even for just infinity use. I carry both sets of bellows (std and AC-254).
If you don't put the limit screw back in to the rail, you can slide the rear standard off the rail if you prefer.
Not sure what the value is of sliding the rear standard off the rail. Perhaps you could explain?
A separate, smaller system involves the Novoflex BALPRO T/S. For my work, this system was poorly designed, because to stack photos optimally for stacking software, we want to FIX the front standard and move the camera with the rear standard. A second best method is using the focusing ring on a standard lens, and the least optimal is using a focus rail and moving the whole camera/lens.
Well, the BALPRO allows you to move the front standard (T/S) area, but has no focus knob on the rear standard, where I would like it. Sad. So, I mount my lenses to the BALPRO on the rear standard and move the camera/front-standard to stack photos.
The length of the bellows on the BALPRO is 200mm (7.9”), which is just enough to do some things. To gain a little extra distance I use a wide Nikkor extension ring like the PK-13 (27.5mm) on which I mount the camera. The BALPRO, for all of its imperfections, does offer a relatively inexpensive bellows system for mounting a DSLR. I imagine that I will be able to mount the Fuji GFX on the BALPRO using something like the Fotodiox Nikon adapter and have an instant mini-technical camera. Novoflex makes many adapters and the Rollei X-Act 2 boards fit the BALPRO (and vice versa).