When I installed my side skirts I used the 3m tape first and then secured it in place with the factory clips that go underneath. But most importantly to hold it inplace in my opinion (3rd and final step) are the screws that should be mounted behind the rear side skirts where the old mud gaurds used to be. If you use 2 screws back there and 2 in the front that go into the plastic fenderwell area just behind the front wheel that should keep them from coming off. I've had body kits on 3 other cars and they usually bolt or screw into these same places on all of them. Let me know if you need pictures. I can take some this weekend. Hope this helps.
