Need a Tonneau Cover

I intend to full-time. So for the winter months the 5th wheel would be pretty much stationary. Ideally, during that time, I would want to be able to keep the bed covered and the hitch and aux tank protected from the elements. If I had a hard cover, something like a BAKflip or a Fold-A-Cover, then I could keep the tank and hitch out of the elements for that entire winter time period. And I could open it and fold it back to refuel the aux tank as needed. I had also hoped to be able to fold back the cover and 'stack' the panels over the aux tank so that the tank would have some protection even while towing during the other 3 seasons. Then I would just un-stack and fold it back over bed while I'm at a campground.