I only know of 2 sailboat owners that use an all roller trailer. One of those two recently dumped the boat in the middle of his street, during some repair and cleaning he failed to attach the winch to the bow eye cleat.
So, make sure your boat is well secured to the trailer!
Mathematically I would say that each roller is offering from 1 to 2 inches of support times say 36 rollers would be 36 to 72 square inches. Where a 6 x 96 bunk times 2 would offer up to 1000 square inches.
Mechanically one would think that loading and unloading would be much easier but, during launching the boat would have to be floating before unhooking the winch from the bow eye, unhooking at any other point on the launch ramp would mean an instant launch. As someone else has suggested, loading would require still floating the boat on the trailer, that bow eye was never built to lift that much weight even on rollers.
Over the years I have helped launch and recover each one of these boats in the attached picture.
