rear overiders appear on most cars to be bad and warped
i tried making a glass replica (still have the mould ) but bever actually went very well
i ended up using a set that came with some parts i aquired ,still wrinkled and out of shape
i ended up using an air sander (6 inch ) and started out with 120 grit paper and not much pressure sanded out as many of the imperfections as possible ,the end result is a set of overiders that actually look decent
worth a try to make your car look decent from the back