@Noddemix . for ease of use, attaching the lens instead of the camera can make life much easier. As far as having to re-level goes, there are two ways to reduce manual effort be either building a very stable rig or by using a device that helps to adjust easily.
Stable
- Let's see your DSLR film scanning setup! - #56 by Digitizer
- Let's see your DSLR film scanning setup! - #336 by Digitizer
Easy adjust
You start with a Kaiser copy stand. It should be easy to mount your gear to it with the least number of components. Attaching the lens as directly as possible reduces flexing and vibrations. The farther away the lens is from the column and the copy stand baseplate, the longer vibrations can last.