A lot of work there !!! I fitted the exact same horn but in a different place. I removed the right hand side long black plastic panel - the long thin panel underneath the right handle bar. I mounted my horn in the ample space in there with no problems. The wires powering the orginal horn even reaches by pulling them back up through the cable ties, so no need to extend cables or anything. Full job from start to finish 20 minutes.
If I knew how to post pictures I show a picture with the horn in place.
Dont ride faster than what your Gaurdian Angel can fly