This is getting into a lot of what I don't know-but what I think MIGHT matter-----Old Man Emu makes a "small" lift kit (2.5"-3"). I realize you don't want to lift it -however one of the "options with that kit is the choice of springs. It was originally for if you were someone who may have changed a lot of the components -- like bumpers, heavier spare tire, winch, jerry cans, high lift jack, on board air etc. Also hard or soft top.
By being able to get a stiffer spring-and knowing that ride is better with the OME kit (I speak from experience) maybe it would also help with your ability to tow the boat? And maybe not too saggy / better control? IDK just a thought.