I don't like the flimsy external ears, either, and the last time I mounted one of those using screws from the inside, I discovered that you don't have to drill the box at all.
There are two countersunk indentations inside the back wall of the box, with matching tiny conical points on the outside. A firm tap with a hammer on the point, and you get a nice, clean breakout for a #8 flathead screw. A dab of silicone before driving in the screw seals it nicely.
All you pros probably already knew that, but it was an "Aha!" moment for me.
