So you can't have the canopy because it doesn't come with stamped structural drawings? This is what I plan on putting on the side of my driveway once I get another small strip of exposed agg done.
http://jawportablebuildings.com/
In the meantime what I've done and I find it to work pretty well is just a 15'x30' tarp. I pull it over the boat with the tower up. I still pull my boat cover on as well and leave the sides open when it's dry so it can vent or get some fresh air. If it rains I strap it right down. I use four big alligator style clamps and 2 bungie cords.