Besides the number of feet you can fly is the force on the equipment when it reaches the end and jerks. There are many stories of sailors being ripped out of the harness and the only thing found is a broken strap. We also have a double tether and a padeye on each side of the cockpit coaming. A 6' safety harness strap has a lot of force from a 200 lb man flying around the cockpit. Better to have a double and restricted movement.