Just wanted to post a few pics of my air horn install...
I took a few measurements from my 300 based on where I figured I could attach the horn and where I wanted it to mount up (away from wires, the engine and fairings), went to Home Depot and picked up some steel "corner bracing", I got lucky and it fit perfectly on an existing bolt...
The horn couldn't attach directly to the brace because of the size/shape so I used a piece of flat steel and some hard ware to attach it (with blue Loctite)...
After a few test runs it seems great so the next time I have the fairings off I will add an additional piece of flat steel from another hole on the corner brace just for extra strength.
Side view...
I purchased the Universal Plug-n-Play Wiring Harness for a quick and easy install, I routed the wires down the side of the bike to the battery...
All back together you can just see it through the fairing...