Hi Matt
Considering that the OEM horn is actuating when running the output test via the GS-911, it could either be a wiring change (to connect the horn button to the appropriate wiring to trigger the horn) or a software change. We unfortunately have not done this before, so unsure whether that's possible.
If this is something you'd be interested in working with us to test it, send through a full autoscan to support@hexinnvate.com and I'll check with the developers whether we can look at a remote session with your bike to get this checked/logged.
Kind regards
Ruan