[ptack]

Sounds like a good way to damage your car in the first storm. Basically, if you want a structure it better be strong enough to withstand some wind and as soon as you start holding up sheets of plywood, you're talking serious force. The only thing I would do that might be relatively inexpensize would be a car cover. A Rhino shelter might be ok if you know what you're doing and know how to reinforce and anchor it.