I have made RV Trailer covers out of Sunbrella and Weathermax 80. Both work exceptionally well and both need similar protections and venting features. Both materials are subject to chaffeing so you will want to provide a "rub" patch at wear prone points. They both need ventilation. I provide this by using highly breathable fabric patches at a couple locations at the highest points of the cover. As air inside the cover heats, it rises and these breathable patches provides exit points for the warm air. Like a chimney, warm air rising and exiting creates a "draw" of fresh air to replace the exiting air. This chimney effect helps keep condensation from building up, reducing possible mildew or mold problems. I've never had a problem with mold and mildew and I live in hot, steamy south Texas.
Mojo's comment about light weight has merit because these covers can get very heavy and hard to handle for anything larger than a pop-up. That said, the weight and handling is a trade-off I'm willing to live with to get 10 plus years of life out of a cover.
Mojo's comment about light weight has merit because these covers can get very heavy and hard to handle for anything larger than a pop-up. That said, the weight and handling is a trade-off I'm willing to live with to get 10 plus years of life out of a cover.