A few days ago I undertook the installation of a Stebel Nautilus air horn in Rubina. I had already installed the MCC Cruise Control, the current version of which has the electronic actuator.
The actuator unfortunately crowds out the space we used to put the Stebel in so I had to mount the horn lower, on the same hole the original horn uses.
That works, in that it fits inside the cowl, but it prevents the inner cowl from being fitted. That in itself isn't a problem because a few owners remove the two inner panels in the belief it improves the airflow hence giving the rider a cooler ride in summer.
This is what the installation looks like:
We used to put the relay on that hole but I had a failure of a relay there due to water ingress. Of course its waterproofing can be improved, but in any case, I mounted the relay above the horn. That's the red box. If you look really hard, to the right of that relay is the black relay for the LED driving lights. Oh, and for Brookster, that blue wire attaches to the blue wire at the headlight for the LED relay trigger. The high beam wire is blue on both headlights.