Mike and I both had the same issues with the skirt just not sticking to the car even when prepared properly. So I recommended rivnuts. They are basically rivets with threads in the middle to put a screw into them. I used them all the time in the Navy. Mike bought a set for about $85. It came with the rivnut tool, rivnuts and screws.
See the gap after a few days
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Drill a pilot hole at the spot desired to allow for the greatest fit. Test area by pressing with your finger to see which spot provides the best pressure to hold the skirt against the car.
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Remove the screws close the area you have drilled the hole.
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Drill and debur the hole for the rivnut, the drill bit size that is specified by the kit must be used. Step drill up to that size. Then debur the hole. Do not use a file to do this.
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Touch the bare metal so it doesn't rust
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Using the rivnut tool, compress the rivnut until the tool begins to get hard to squeeze. Too hard and you'll rip the threads out.
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Rivnut installed.
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Paint the head of the screws (provided) to match.
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Re-assemble and tada.... Mucho better
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