I didn't have to do too much. I bent the GTS stock horn mount back a bit to accommodate the larger horn, and used the straight bar that mounts the horn on the X9 to offset it a bit so that it would fit well. I kept the rubber grommet to absorb vibrations, and it suspends well in the cavity without touching any part of the body or coolant lines!
All in all, a simple, worthwhile mod.
~Drew

stock horn

X9 Horn