Alan, my understanding of having the boats on the hulls is that when the trailer torques, flexes or bounces, all of this is transmitted through the brittle hulls onto the boat. If the boat is hung the beams suspend the hulls clear of all this and it is absorbed by the beams onto the strengthened parts of the hull.
Mine used to be on the hulls but now a c section surrounds the front beam with a large bolt into the mast step to keep it in place. It still rests on pads aft but the fwd beam has 80% of the weight anyway. I slide it onto the pads, lift it up an inch to slide into the C section and screw down into the mast step.
Also makes it a lot better on your boat if you want to stack 2 boats.