Well...for the price you are going to pay...
you might as well get one of these...
http://cgi.ebay.com/ws/eBayISAPI.dll...332022558&rd=1
I was going to get one of these, before I got a military tent.
I don't know if you plan on working on it while it is parked...but this would
be your best bet, in my opinion. There are a few guys that have it, and I asked them. It isn't GREAT, but like I said I think for what you are looking for
this would be your best bet.