So, I had a go with MG IV RC using a small lamp bounced off the ceiling [direct light was far too bright]. Exposure times were too short to be useful -- somewhere between 1 and 3 seconds, depending on the density of the negatives, and a second either way made the prints unusable. However, as a trial run the rest of the process worked fine. No newton's rings, the workflow was straightforward, and I was able to temporarily light proof the room easily.

Thanks for the advice. I'm going to experiment with finding ways of reducing the intensity of the light [for the MG IV] and also seek out some slower paper.