What would you consider as "good weights"? I don't think a boat would bother me, but a pontoon boat would be more of an issue IMO. Higher, heavier, more wind catching area, more of everything. As was mentioned a lot may depend on how much distance you're looking at. A few miles wouldn't be a big deal, halfway across the company, maybe not for me.
My brother-in-law pulled an 18 foot vee hull behind his 30' fifth wheel from central Iowa up into Minnesota for quite a few years with no issues. One year he got stopped by a over eager hiway patrolman who informed him he couldn't go into Minnesota. Turns out the regulations mandate that the first trailer be a 5th wheel no longer than 30'. He thought he was fine but the LEO informed him his 5th wheel measured 30'6". Too long.