the piece of metal is ghetto as is. I'm not going to make it more ghetto by hoding it in by screws. If I were to make holes in the bumper it would be for a good reason. Like putting ABS in there instead of the metal piece.
Yeah I was thinking the same thing with my xB looking inside the rear wheel well. The air may just leak out the bottom and closing it off would maybe trap the air. Now you have to think about opening up a hole in the center and let the air out. Turbo air exhost port. Time for some streamers to see what is happening with the air flow under there.