I just purchased a 76 Airstream (my first). It has a great exterior and I would like to keep it that way. But no garage or carport. I am thinking of ordering a custom cover for when trailer is not in use, but dont know if this would be more harmful to the exterior, than being left uncovered. Any one tried the covers that are Tyvek on the inside with a poly coating on the outside? Any comments would be greatly appreciated.