If you are thinking about a fabric-type cover, you might want to consider that they frequently cause more paint damage than they prevent. Putting them on and taking them off frequently results in dragging the fabric over corners and edges of the coach body with the potential for scuffing the paint. And, once on, the wind will move them around, scuffing any high point they rub on.
A good wax job provides nearly the same level of protection IMO. Just my $.02 worth.
TJ