This suggests that the R and RS are identical fittings. You will find fitting instructions here.
MV Verholen have been going for years and make some amazing stuff, including electrically adjustable handlebars for the K1200RS (>£2000). I have wondered whether thay manufacture for others.
Thanks, I know the mounts on both bikes are the same, just that I would rather not pay Wunderlich/verholen etc prices if the GS or RT ones on eBay for £45 will fit.