Pulling a 5th wheel RV trailer with a 1/2 ton.

If you ask me you're asking for trouble. Pure white knuckle driving with an over loaded truck. lol
I have pulled everything with trucks, horse trailers, 33' twin engine boat, campers, 5th wheels , car haulers etc.
I prefer a 1 ton for all towing. A 3/4 ton is workable in most situations and 1/2 ton is good for towing small campers under 25'and small boats under 20'.
When towing you want to be safe and comfortable with reliability.