PIAA Bracket on R1100RT
This is the final product. PIAA lights are mounted below brackets, below the mirrors. The bracket had to be very carefully crafted to fit around the design of the reverse side of the mirrors.
While this works ok, there are issues, and I suggest that you not use my exact solution. I wanted to avoid removing the dashboard or fairing. A better bracket and bracket mounting is easier to make if the dash (and/or) fairing are removed.
First off, with the dashboard off, you should be able to remove the mirror studs and use them to mount the bracket. I think that if you mount the bracket behind the studs, the mirror will be clearanced further from the fairing, but only to the thickness of the bracket. That's small and shouldn't create a problem. As far as I can tell, the "above mirror" bracket seen on other sides relies on this mounting. I think the ideal below-mirror bracket would bolt to the two lower mounting studs. It would be a simpler, stronger bracket.
Second, the wire routing I used is not idea. It was tricky to route, and the wires are pinched. Routing via the vent may be a fine idea (if the visuals don't bother you), but pinching the wires is bad. It might be possible to drill a hole in the vent pipe/duct inside the grille where it isn't visible. Run the wire through that hold (maybe even with a grommet!).
As for switching, I used the original owner's switch. He installed a weather proof switch on the dash with an LED. The PIAAs only come on with the high-beams, and only if the dash switch has also been turned on. The LED is green for no PIAAs, and red for PIAAs on.
The original mounting position was below the oil cooler. The big problem there was that every bump and driveway apron that caused the front forks to compress also smashed the front fender into the PIAA cases. Not ideal. The fender and the PIAAs are permanently marred. In retrospect, both the original owner and I are surprised that anyone recommends the 'under oil cooler' mounting position.