I have one of the Adco Sunbrella covers. It's really nicely made and heavy duty. We bought it for our 36' DP and rarely used it. It's soooo heavy that it's difficult to put on. I would only suggest buying one if you need to cover your RV for several months, like winter storage. Ours is like brand new and is in the original bag. It won't fit our new coach.
Since it was originally so difficult to install, I bolted a large out door plastic garden box (from Home Depot) atop a rod iron fence that I back my coach up to. From the roof, I could pull the cover out of the box and drag it into place. It was just to heavy to pull it up each time.