Ditto on boat trailers having less tongue weight than other trailers.
I figure out the boat aerodynamics prevents the trailer from fishtailing, you'd have with square trailer.
I would love to see a picture of 7k lb boat behind TC.
The heaviest boat I had was 25' cabin cruiser, 102" wide, with toilet and water tanks. That boat was less than 3600 lb, or about 5k wet on the trailer.
I overloaded my SRW trucks with construction materials almost every day, but having tall TC on overloaded singles - I could not shake the vision what might happen after tire blow-up and bought dually within few weeks.