Don't know if you have them and took them off or not, but someone posted on here where they mounted the lever flush on the midframe heat shield that looked pretty slick.
Thanks for all the ideas. Sounds like I need a die grinder. I agree that shaving the hole open a little more will not affect the frame integrity. This is the location these are designed to be installed, just into a separate bracket. The bracket isn't sold separately, i believe it's part of a kit that has all the hardware for the adjustable back rest, and I didn't want to pony up for the kit.
I do like the idea of picking up a heat shield and mounting in that instead, I'll check that out before I start grinding..
We mounted the same kit on my friends 07 SG, in the hole you are talking about without modification. Don't remember how but I think the main obstruction was overcome by routing the cable.