I think it will be quite OK as the dimensional difference allowed for by the shimming for the RHS caliper are very small.
I'd measure the clearance on the caliper as it is now, then remove the wheel, flip the disc and refit, then I'd measure and if the differences were small I would ride off happy.
I have fitted dual caliper systems to 3 R65s now, firstly to my wife's bike, thne mro erecently to bikes owned by others. I have never actually held one of the RHS caliper shims and frankly I only know of them through this group. None of the R65s I converted to dual caliper have had the slightest problem.