steve, not sure if you saw this description at the bottom of nippys page
"The installation is rather straight-forward once you get your head around the fact that there IS in fact enough clearance for the horn using the OEM horn location. The OEM metal mounting strip is a bit wobbly but in six weeks and 1,500m nothing has moved. I might fabricate a stronger one when I find the time.
The only tricky bit was the CANBUS connection to the horn: it IS polarity sensitive, so if it only quacks like a sick duck rather than sounding like a fog horn, the wires to the horn need to be swapped. I used a 20amp fuse and fixed the relay to the frame with a cable tie. No wires were cut and I used connectors where necessary so the bike can easily be returned to its original condition. "
might be of help.
cheers
mike