I agree that having the harness attach at the waist would make it difficult to recover if beign dragged.

I think Pete is working out a system for a boat much smaller than the 20, and I believe that he would be able to effectively stop his F16 if he were to fall off still connected to the maisheet/travler arrangement.

If the harness were designed in such a was as to drag you on your back facing forward (like a parachute riser), you'd (1) not get held under water (2) be able to utilize a quick release if necessary and (3) maneuver back to the craft using the lanyard.

Perhaps there is another way to disable the boat (preventing it from sailing off) if you fall? Maybe some sort of rip cord that unlocks/pops the rudders (like a kill switch on a powerboat)?

Could anyone show what happens to a uni/spin cat when the rudders are popped (1) upwind and (2) downwind.

For the purposes of this experiment, you'd have to let go of the control lines to simulate you falling off the boat. This would likely mean that the main/traveler remains sheeted, and the spin released.