I would not carry expensive bikes out side unless absolutely necessary. I carry my bikes in one of my pass trus by removing the front wheel and seat and tilting the handlebars flat. If I bought a smaller unit like a 24 ft Class C I would look for one with a large storage bay in the rear and store them there. As a last resort if the MH had little outside storage I would get a custom cover like the grill cover you mentioned and add snaps on it to snap to the bottom of a carrier to keep the rain off and keep the cover from flapping.