I have been doing this kind of horn mounting for at least 15 yrs & have never had one break or come loose yet. Everything from fun fly, scale war birds & 1/4 scale pylon racers. I first cut a groove into the moving surfaces leading edge. Then cut or trim the horn to fit inside the pocket formed by the groove. At this point, the fit is kind of loose which is what you need. Next I ruff up the horn surface that will be inside the pocket, then fill the pocket with 15 minute epoxy & fit the horn inside & Adjust its fit with flat tooth picks shoved into the pocket to help keep everything aligned as it needs to be. Wipe off extra epoxy as needed & when dry, you have an almost indestructable mount. And it is invisible from the top surface. Bill