I would get a free standing roof type cover instead. Car covers, when used outside, trap moisture rising up from the ground under it. I use a sealable "pocket". I set it up, back my car into it, put a car cover on it, zip up the "pocket" with dessicant inside, and put a tarp over that. But my car is inside so the wind won't make anything slap at my paint.
Just a thought,
Scott