@Graham , I like the wooden contraption you (had) built…thought of doing something similar for a while.
@rh_photo , for (645) film strips, the camera (and rail) could be rotated 90 degrees in order to allow the film strip to not interfere with the vertical column. By replacing the dovetailed L-boards with a simple flat board this could be achieved with even less woodworker skills. In comparison, your copy stand looks shaky and vibration happy. No need to change the build too much though. Simply remove the ballhead and attach the camera (on a rail if you want easier focusing) directly to the clamp. An L-shaped baseplate could be used for easier film handling…and I’d remove the camera strap while scanning.
For best alignment of the optical axis, use a mirror as shown here.