Mine is mounted on the clutch reservoir, using a bracket sold by an old Forum member who isn't active anymore (either on the Forum or as a fabricator). It's a round aluminum disk, about 2mm (1/8") deep, and perfectly sized for the bottom of the GXM-30. You remove the screws from the clutch reservoir cover, put the disk on top, and then screw it down using slightly longer screws that hold both the bracket and the original reservoir cover in place. The disk has holes on the bottom that match up the the little threaded mounting holes on the bottom of the GXM-30, and you use screws that pass up from the bottom of the disk into the bottom of the GXM. It is a totally secure mount, and it's a huge pain to remove the small screws that hold the GXM onto the bracket without the right tool, so you don't have to worry about anyone removing the GXM from the bike. (Even with the right tool it's still a pain.)
It works really well -- with the V-1 on the brake reservoir and the Zumo on the steering nut, everything is far enough away from each other that there's no interference, but still within easy reach, and with nothing to obstruct the XM signal.
Unfortunately, new ones haven't been offered for almost 5 years now...
