Hmm, UV transmission through RC paper is probably going to be pretty lousy.
Say, can you make a wet contact print? In other words, wet the neg and the print paper with plain water, sandwich them between glass, and then expose? If you squeegee out the bubbles then you may (I repeat may!) see some sharpness and exposure benefits. I am thinking that the water may increase the UV transmission of the paper. (I use plain water with immersion objectives in my UV microscopy)