I finally mounted the horn. After much analysis, I agree with the others- there really is no great place to mount it. Further, the only place at all appears to be under the right fairing. Fortunately, although it was a nightmare getting all the panels off, mounting it was a piece of cake! I just happened to have a perfect mounting bar of metal. I drilled a hole in one of the triangular fairing support brackets and used a bolt there to hold a strong bar. It it fairly straight, but with a slight tilt. It holds the horn in just the right position. I have attached three hi-res pictures for those trying to imitate.
I did use the optional wiring kit, which was very high quality and made things easier. I did modify that harness to keep the stock horn enabled, which I like as a backup or just even more sound. The magnetic horn enabled is also nice when you have to perform a micro-beep for times you need to remind someone of a light... if you are fast enough, you get a beep from the magnetic before the air horn can wind up. Perfect!
OMG, the Nautilus Compact is a LOUD horn.... especially when mounted this way (because the trumpets are pretty much aimed AT YOURSELF!