The MA Shaw piece actually has a very small vertical lip on the under side.
There is just enough material on the bottom of the bumper to add a OEM RUF lip or a piece of conveyor belt which all the factory RUF air dam is. But there isn't enough material to easily add the air dam with a hidden attachment.
Top of the bumper is just flat and takes no smile. Not the best picture but the top of the bumper is pretty clean instalation.
