I installed the Stebel air horn on my Cobra engine guard of Vulcan 900 and it all went very smoothly. I appreciate the tips on your posting and especially the photos. I did tweak my installation a bit. First I put some paper over the OEM horn bracket plate when I clamped it down to the work bench to drill out a larger hole - thanks for showing how easy the bracket can scratch.
I also installed the bracket plate on the inside of the cobra guard bolt and tightened the nut against the plate so the horn is just a bit more flush with the bike. The wiring was a breeze with the instructions and wiring that came with the horn from BikerHighway.com, although I did go out and buy some black 14 gauge wire and L shape connectors since the positive wire to the relay supplied by BikerHighway was red and would have stood out like a sore thumb. Anyway, thanks again for your great original posting.