This might be a little late, but better than never (i hope).
There were two choices that I had.
1) I could have done a direct replacement by taking the stock side skirt off and replacing it with the ACS one.
2) I could have had the ACS one fully over the stock side skirt.
I went with direct replacement since it's lighter that way and it doesn't somewhat bulge out.
Mine's has never had a problem with it and it's been about 3 months so far.
As for the rear, that's glued onto the stock bumper, but I don't know how (if you felt the need to part out your car or something) to remove it after it's been glued.
As for the front, I have no clue... I have a Rieger front.
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