I have a 2013 Tundra DC rated at 9,500 lbs tow capacity and pull a 7,600 lb 32 foot TT. Truck has 14K miles and fully 6K of that is towing. Just returned from 4,400 mile trip to Utah.
The Tundra has done everything we asked it to do, at over all 9.1 MPG average towing which I don't think is bad for a gasser. True, we didn't pass many diesels going up the side of a mountain, but we never dropped below 55 MPH nor above 4K RPM.
Yes the 26 gallon gas tank is too small for towing, but as you get older you will find the tank and bladder capacities start to match up with each other.
PS - Last time I looked it up, Tundra was the second-most US-manufactured truck behind Ford.
But have to agree with almost everyone that commented - the payload capacity of the truck is very small for something this strong.