I have made paper negatives from prints it works pretty well, as long as there isn't writing on the back of the paper. use the brightest light possible to make your exposure ( contact print ) I never used to do this but now I do .. take the lens /mount/board off of your enlarger when you are making your exposure, you will need the light. sometimes I like to get my paper wet ( receiving paper too, and squeegee them so they make a good tight bond ) when making my paper negative, sometimes it works sometimes it doesn't. rc paper is thinner than FB you might have better luck, but still FB will work. I have a stash of single weight paper that I sometimes make my internegative with or I use hand coated ( home made or liquid emulsion ) on thin paper... some Japanese papers are SEE THROUGH just about when waxed so that might also be an option. I also use the electronic thing and wax that paper as well, works great.
have fun!
John
