After some 34K-miles towing a light travel trailer, less than 2900# , at the end of June I towed a 5100# trailer+boat combination and was super pleased with how the V6 handled the job.
Highway speed was kept in the 55-58 MPH range with Tow-Haul engaged and 8-speed "L limited' to 6th gear. That was done for my comfort and to help the fuel mileage which was 14.2 MPG. Hand calculated, the truck was reporting 15 MPG over the full 300 mile trip.
CatScale data with full gas tank and some gear in the truck bed:
Front Axle . . . . 2600# on GAWR of 3200#
Rear Axle . . . . 3120# on GAWR of 3500#
Trailer Axle(s) 5100# on GAWR of 6000#
I did not measure tongue weight;
Travel Trailer removes the rake so when towing the truck is level,
Boat dropped another 1-inch lower than front. axle center to fender top center.
Picture of rig (low tongue due to a Drop-2 hitch ball, I have since moved to a Rise-1 hitch ball)
Elevation of I-90 crossing Cascades, west to east:
And because I have an Extended Cab, the 6-foot step ladder needed to board the boat is safely in the
cargo box not sticking out - - - - so wish the 3rd Gen had an Extended Cab option.