If you look at the pic in your instructions (fourth pic form the top) the horn in the back ground, you have mounted to that little piece of metal with two holes in it.

The hole further back is the perfect size to mount one horn. The second hole is not. So instead of looking for somewhere else to mount it, I used a smaller bolt to mount to the smaller hole.

Both face downwards, so I hope they'll drain. But honestly, I'm not all that worried. And to be totally honest, I almost never use my horn. And every now and then, it didn't go off anyways.

But things are good.

BTW, I got my OMP STB today while I was doing the horns and an oil change.

I'll be sure to check out your site one more time before I try installing it.