David & all, As far as I know, there is no adapter to mount a "R" series, or for that matter, any "M, or Screw" lens reversed on a Leica Bellows. Now, with that being said, about 10 years ago I did what you inquired about, I "Made" a reverse adapter from a SL body cap. I cut a hole in the cap, large enough to accept a 49mm reverse " Macro ring, the male to male one, but made for a pentax. I mounted a 50mm 2cam summicron in reverse. I used a 44mm (basically series VI)-to-49mm step-up ring, then screwed the male-to-male 49mm into it, stuck it through the hole in the body cap, and locked the exposed threads in place with a 49mm filter that I had removed a very scratched filter glass from. I sealed the entire outer ring in place with black, silicone caulk, to both lock seal it and seal off all light. I then mounted the body cap/lens combo on the front of a bellows R, and shot away. The advantage of the series VI ring, was that I also had an earlier version of the 35mm f/2 Summicron which conveniently used the same ring. However, if you are lucky enough to have a 2cam "U.S. Navy" version of the 35cron, it already was modified to accept 49mm filters by Leitz, per USN specs. I was "talked-out of" the homemade adapter rig by a friend of mine who offered me an obscene amount of cash for the 35, 50 and mounting rig, ($1,000.00, and that was 1993 dollars). Oh well, I never got around to making another one. I also used a Cokin flash, the one that is multi-dedicated and has 3 rotatable flash heads & mounts on the Cokin "A" system adapters. I kept the flash, and still use it regularly on my (GULP) Kiev 60!, with great results. Hope that helps. Art