How long have you had your car?? Well when I use to work on cars, Lin/Merc dealership we would use revots and first drill two-four little holes into the bumper then rivot the holder in place so it wouldn't go anywhere. The bumpers i worked on had two little indents that showed where to drill. I dont like audi does that but pick a spot right under the rings and drill away!

 

i got it in october... so about 3 months... its my first audi, so i'm pretty new to it.