I have experience with hauling that goes back more than ten years. I have been hauling farm and earth moving equipment on a flat bed trailer for the past three years, as well as dump trailers (to move dirt).
I don't have any references, as all of my work has been for family and personal reasons. I would give you my father in law's number, but he's a little bit biased (in my favor).
How have I pulled boats in the past? To be blunt, I haven't ever pulled a boat. I've spent more time being pulled by a boat. But (I know this is blasphemous to say) the same principals apply to hauling cars as to boats: secure the load and drive carefully, both of which are things take very seriously.
Please let me know if you have any other questions, and have a good night.