I'm not so worried about the simple act of drilling the car, it's just plastic anyway. I am worried about how difficult it is to line up correctly. Drilling is pretty permanent, and an error would be forever.
They are pretty flexible, lining them up is no biggie. They will only fit the side they are designed for... Front and rears are different...How hard is it to orient the flaps correctly? Do they only fit one way, or is it harder to line them up to make them all look the same?