Going back to the original topic

The steel racks made for commercial trucks work great. There are many varieties and options. Make sure they are installed properly and pay attention to how many racks (2,3, or 4) are suggested. Check to see if there is a local supplier. The ones in Houston don't even look at you funny if you say you want to carry something ~200 lbs and 30 ft long (they may say "that a lot of ladders")

My only suggestion for supports is make sure you can rest one end of the boat on the rack and the other on the ground without hitting the truck. This will allow 2 people to load the boat.