Used a cover on my previous fifth wheel for a few years, never any damage I could see. Friend covered his on 'MY" recommendation for one winter ,terrible rub marks . He had it tied down pretty well. One of my sons covered his motorhome ,same results some bad rub marks , never covered it again .
Not sure what the difference was with mine , other then the fifth wheel had four slide outs with toppers that held it way from the sides a bit at the top . The front ,and back caps were subject to rubbing , but never seen any dull spots or rub marks . I did wrap the rain gutters to prevent any tearing of the cover .