I towed 4.5k pounds f(15BH) for 6k miles last summer with the same truck. It was completely effortless, even climbing around in the Rockies. The power was there to jump out in the passing lanes if I had chosen (I didn't). The truck led to us upgrading trailers over this winter. I'm now towing 5.5k dry, 7.5k loaded. The truck does downshift once in awhile now, but still feels very strong and well within comfort.
I did not use WDH with the old trailer. There was never a moment of sway. I do use it with the new trailer.
