Although I have an adapter to mount a camera on my old F30 Durst enlarger column, I think I would hesitate to put something as heavy as an RB on it - too much chance of flex. The M605, maybe. The whole point of a copy stand is to have stability and parallel alignment. Modifying a Beseler 45 looks like a non-trivial job, unless there is a way to do it with the system stripped down to just the negative stage and no lower bellows. If I was going to do that I'd probably just mount a shuttered lens on the enlarger and copy onto 5x4 sheets. I can even see a way to use a Calumet rollfilm holder in the negative stage, but I admit I have not offered up the parts to test it.