[Carno]

I personally dont really see how this would help in lowering the car much but I have had an issue where the front of the undertray got dislodged from under the bumpermount, bent back and ripped off.
Thus forming a very nasty extruding bit of lexan that digged into the surface on braking/landing.

Currently I managed to cut off the back of the bumper just right so the undertray fits and stays in place.