Pool noodles, pipe insulation and tennis balls strategically placed over sharp edge and "pointy outey" things keeps from ripping you cover.
The better ones use tyvek or another breathable membrane on at least the top portion.
Get it snug to prevent wind flapping, which can abrade corners.
I just ordered a Camco cover for my TT. It has flap openings the supposedly reduces wind lift.
We shall see if that's true.
My TT has fiberglass/plastic end caps and I plan to try some decent thickness "cling wrap" on the corners to try and give a little extra protection from wind rub. Kind of like the stuff you see on new cars when they are delivered.
Throw in some tire covers while you are at it.....
2011 Flagstaff Classic Superlight 831RLBSS "Atrium slide"
Husky Centerline Hitch
1998 GMC Sierra SLE K2500 6.5 Turbo Diesel