The Stebel is in and WOW! It is amazing - couldn't ask for better/louder!
I couldn't mount it high up under the speaker area as per the US-site's instructions as I have a Seng light bracket in the way (for the PIAAs). The bracket uses the 2 bolt locations suggested for the Stebel. So rather than try to split the horn into 2 pieces, or to mount it on the left side of the bike, I decided to try to get it lower on the right side close to where the OEM horn sits.
Mounting the Stebel lower on the RHS allows its air outlets to sit directly adjacent to the slots of the inner cowl where the OEM horn sits - meaning the sound escapes beautifully from the enclosure of the fairings. To do this I first removed the OEM horn together with its mounting bracket.
This leaves the tubular subframe extension with a single bolt hole in its flattened end. I then used vice grips to crush/flatten another 30 or 40mm of this tube, allowing me to bend it up at a right-angle to take a bolt through the Stebel's mounting point. The trick is to end up with just the right length for bolting the horn the bracket.
I cut the small locating tab off the end of the bracket (and filed it clean), then drilled another hole closer to the end of this bracket (between the existing hole and the end - so no excess bracket is sticking out past the side of the horn). A bit of black spray paint to touch it up, then bolt it all in place and attach the wiring. This first pic shows this and how I used a vertical bolt rather than the larger horizontal bolt that came with the horn:
These two pics give a better overall view. Note the separate heavy gauge power (red) and ground (black) to the relay. The power wire to the relay feeds directly from the battery with a 20amp fuse located at the battery end.
As can be seen above, it is pretty crowded inside this left-side fairing, but I was reasonably confident the fairings would all slot back into place without any real problems. I used to have twin FIAMM "highway blaster" horns located in the same spot as the Stebel, and it took quite a bit of fiddling with the brackets to get them to fit in the space, but in the end it was okay and as the Stebel horn is no bigger, the fairing and cowl fitted back in place beautifully.
So don't copy this mount yet until I check it all fits !!