Spraying 303 Aerospace Protectant on cover will help to protect it too from UV madness, probably will need to much of the product to cover the whole cover. This product is a UV inhibitor SPF 40. Been spraying it periodically on a 380 sib which has red tubes living at a marina, in 3 years have not lost it's original color and tubes fabric looks like new.
You can buy this product at West Marine, Defender or other reputed boat stores, for what it protects it's a cheap product. Can be sprayed on vinyl, rubber, plastic. leather, fiberglass, just follow instructions.
Double layer plastic covers glued between them are no good, will blister, hardly lasts 1 year. Better are thick heavy duty one layer covers, check the heavy duty one being offered.