I like using the well-built Omega enlarger negative carriers for holding 6 X 6, 6 X 7, and 4 X5 sheet film in place. For unmounted 35mm, I use a pin-registered holder (Marron Carrol). I use a "slip" stage for mounted slides; one I salvaged from a Forox.
I used to do copy work with a multi-shot MFDB, a 120mm lens, and a 26mm tube. I have an extremely robust copy stand. For a light source, I use a highly diffused strobe. The studio is on a 2' thick concrete slab floor. The setup is extremely stable.
The MFDB copies were outstanding! About as good as as a drum scan.
I still have the same rig, but the MFDB is long gone. I've used the rig a few times with a Nikon D800 for copying B & W negative film. It works much better than an Epson V750 flatbed scanner. I shoot RAW. The workflow is super quick and easy.
Copying color negative film is a chore. A lot of times, the dyes will have shifted and CC is challenging.
Don't get too picky about depth of field and diffusion. If you use a high-quality macro lens like the Nikkor 60mm f/2.8 micro G, you'll be fine. That lens focuses down to 1:1. Setting the aperture to f/8 is fine--f/11 in a pinch. I adjust exposure by dialing the output on the strobe pack.
