I have a 07 F250 PSD and a 35' 10,000 pound 5th wheel, the truck is rated for 15,500.

Granted I live in "flatland" but for the hills that I encounter in PA, the truck pulls pretty good. The only time I got "White Knuckled" was when the road had a pretty heavy crown and there was alot of traffic, I could feel the trailer twisting the truck quite a bit.

I can't see any reason why your truck can't handle the load. If you are uncomfortable with the tow, just stick to short trips on level ground till you can get a bigger truck.

 

The only thing I worry about on overweight trucks is the ability for the driver to haul that rig to a stop in an emergency situation. The Trailer ends up plowing the Tow vehicle and then it's bad for all.

Sorry, but when it comes to towing I stay below the stated GCVW as well as the certified hitch and tow rating on any given vehicle / rig. I don't want to be the one to crush my family or someone else when that thing fails.

There are other things to consider as well. Hitch lifting the rear of the vehicle on an emergency stop / someone cutting you off etc... balance of trailer etc...