One of my camping buddies bought a V-8 Crew Cab Tundra rated to tow 10,000 pounds, and the RV dealer talked him into buying a small fiver, 26.5 Eagle Ultralite with GVWR of 9650 pounds. He also had to buy a automatic slider hitch weighing almost 300 pounds to make the fiver work with the really short pickup box.
He says it has plenty of pulling power, but he is about 800 to 1200 pounds too heavy on the rear of the truck. He has installed helper springs, beefed up the OEM tires to LT in Load Range D, and inflates to 65 PSI when towing. In 20,000 miles of towing he has gone through three sets of tires on the rear of his truck, some of that from fast wear, some of it from throwing treads or blowouts; e.g. even with his "upgrades" he is still badly overloaded.
On the up side, he has not lost control of the rig yet.