I ended up buying a pr of these and bought the wiring from Eddy. It was an easy plug and play arrangement and whilst initially I was in two minds about where the manufacturer wanted them placed, I liked the idea of keeping the original horn in it's place and still operating with these two. Btw, anyone around that gives me the opportunity to use them will know they're in the wrong somehow.
Anyway, I did a long ride with them over several days and haven't had one issue. The also aren't the best looking so being underneath is probably the best place for them.
I suppose the only concern may be some damage from a stray rock or something but I think they'll be alright, especially with the mud flaps a few of us over here have bought.
staffo