I decided it was time to ditch the road runner horn (meep meep) and get something people will actually hear. The SoundBpmb is similar in style to the Stebel Nautilus and Wolo BadBoy, but this one actually works in the long term. I was able to re-purpose the existing horn mount and put it in the same general location as the now removed emissions canister. It's hanging a little lower than I'd like, but until I fab something else up, this will do.
The horn install itself was not difficult. The issue was with the process in disconnecting and accessing the battery on the 821. Holy shit, what a pain in the ass!
I was able to run the wiring along the existing path and into the battery box. There was
just enough room to put the excess wiring and relay in the box under the battery. If I feel like torturing myself again, I may open it back up and shorten the wires. That will probably wait until I decide to go with a LiFePo battery.
Here are the pics of the final install. Like I said, lower than I want, but it will do for now. Its quite stable and extremely loud. I bought everything through Revzilla.
