RAWR = can be the lessor of a tire/wheel/axle and rear spring pack so don't exceed it. When carrying a 5th wheel/GN trailer it changes the trucks front axle very little to non.
I have a 5th wheel rv trailer and have always a GN trailer(s). I keep a hard tonneau or a cab high topper for my trucks. I have a home made rack with rollers in the tractor barn. I back the truck up to it ....and slide the cover/topper off the trucks bed onto the rack.
My son keeps a aluminum Retrax on his trucks. It roll up like a shop door.