Struggled with the mirror question and received good support from here and from available vendors (Santa Cruz) but just couldn't make the move.
I always liked the K1200RS mirrors and even added them to my R1150R (straight bolt on). But they are completely different from the K1200R at the stem and I was conflicted.
Bought a set anyway and spent several days pondering possibilities. The K-R uses a compression fitting on the handlebar that has a 10mm coarse thread base and a 10mm compression fitting at the top that receives the mirror stem...etc
Meanwhile the K-RS uses a bolt through that goes through the handlebar control fitting and is molded to fit while using an 8mm thread and hex nut to secure it.
Still, the wind tunnel designed K-RS has very nicely sculpted mirror stems and I was convinced I could get 'there' with enough thought.
Considered and rejected several options. One criterion was to do no harm to the existing K-R fittngs or handlebar.
Finally, opted for the following (using tools I either owned or acquired inexpensively). I made a complete set of measurements of lengths and diameters using a precision Vernier Caliper and I was cautious to check and recheck my work.
1. Cut about 1.25" from the bottom of the K1200RS mirror stem (which removes the 8mm threaded section and a little more).
2. Using a hand operated tap and die kit, I cut down the remaining stem section for another 1.25" first to 12mm x1.5 coarse threaded, then to 11mm, then to 10mm. Working slowly and carefully, etc.
3. Mated the newly milled K-RS stem to the K-R base fitting and tested the fit, finish, etc. The threads allowed me to position the mirror almost right where I wanted it. Either a lock nut was needed to get proper tension or a spacer at the bottom of the hole to stop the arm at the correct angle to the handlebar. I used the spacer and Red Loctite, after checking and rechecking, of course, to get the arm positioned just so.
4. The result- hard to see because the flash on the pic washed it out some (I'll get a daylight shot soon)- is a lower profile, semi-integrated looking, nicely completed project.
5. The view from the K-RS rectangular mirror is only slightly better, but wider angled. I am comfortable with the result. The look is good.
Not a project for the faint-hearted because there is a risk of harming the K-R threaded fitting and the K-RS mirrors become unusable for other purposes, including resale. But I am pleased.
Last note: I spent about 6 months wanting a different mirror set-up. I spent 1 week thinking about buying the K-RS mirrors ($60 apiece). I spent 4 days pondering the approach. I spent 4-6 hours completing the effort. So this is absolutely not a bolt-on solution.
Thoughts, comments, criticisms?