Thanks for the heads up on the clearance. Learned my lesson when I had my Vegas, the mount I used on it slid down the fork a little and pulling into an establishment the hard edge from the road to the parking lot the fender gave a nice "WACK" and thus the small chip in the top of the fender for life.
I was looking at using the bolt holes in the bottom triple clamp, in between the forks. I've found that some of the hardware on the 15 RGS is metric and some of it is standard, it looks to be about an M8, but I was hoping someone might be able to drop some knowledge on it before I start tearing into the project. Appreciate the pinch bolt info, depending on room I might have to use them instead.