Mirror Solution
Welcome Gerhard and Dirtdreamer:
There is actually a simple solution to the mirror problem.
I had some extra handlebar clamps, which have mirror mount threads, from my R1200R after mounting RT handguards. A similar clamp without the mirror threads is used on the RT bikes, and you can add the GS/RR mirrors simply by changing the top part of the clamp which solves the limited view of the standard mirrors on the RT. I only use the stock mirrors for direct rear view now.
The number inside the clamp is the BMW stock number that can be ordered.
After installation it looks like this:
Notice that I added some stick-on wide angle mirrors to eliminate all blind spots. For those wondering about the toggle switch and the "volume control" knob: The toggle switch activates the RT-P fan installed behind the oil radiator, and the knob is the brightness control for the Clearwater Kristas.
Overall view: