Ed,

As I mentioned I used Chips suggestion of installing the horns on my Double Vision elevators... I have HAMMERED the elevators HARD for fast speed walls and elevators that should have snapped them plumb off...

They've not even hinted of loosening.

You could longer screws on the Edge because the surface is so thick... wick some CA down into the hole to hardeh the area...

OR I suppose a person could trace the base of the horn on some CF or 1/16 hard ply (paint it) and put it on top of the surface, bolting through it completely...

I trust them as is... but you need to be comfortable and not go by my experience.... I've not heard anyone complain of a failure though...

Here is a pic of an install of the horn on a CAP-X...