Just had a thought, re the discussion of puddling and snow *****, etc. I wonder if one could stick a beach ball or one of those exercise balls under the cover? Just big enough to give the cover a "peak", roughly in the middle. Maybe two if one isn't enough.
Ideally, you would have a long inflation tube on it so you could inflate it after the cover was on, so its' not in the way. A long sausage shape inflatable tube going end to end would be ideal, but not many RV's have a clear space down the center of the roof.
Just a thought.....