Thanks for everyone's responses. If the 303 won't harm the decals, I'll give that a try. I really only need to worry about the front and street side, as the back is completely shaded from our trees and the neighbors' trees, and the curb side faces north.
I do need to consider the rubber roof also, though. Will the 303 work on that, as well?
It would be nice to have a shelter, but it just won't work in our back yard. The TT is sandwiched between our storage building (not movable)and our property line. City ordinance won't let us put even an aluminum shelter that close to our neighbors. The trailer sits only about 4' from our neighbor's fence. Fortunately, we don't have an HOA in our neighborhood.
An ADCO cover is another option, but we plan to camp locally on a frequent basis. We have a wonderful state park only 20 minutes from home. I don't want the hassle of installing/removing that huge thing that often. The previous owner gave us his cover, but it doesn't have an opening for the entry door. That's another pain when wanting to access the trailer while at home.