I tried a supermach one when I only had 10 ws jumps, The way the wings are made my arms pin up due to the air pressure in freefall. I managed to scare myself and practice my flatspin recovery skills. I currently jump a pf havok, the wing size is about the same but the wing goes down to the knee resulting in a lot less pressure on the arms. The havok is very stable. I've managed to stabilze after a bad exit doing a ws rodio while keeping my passenger. Granted the supemach one was way above my skill level my arm streangth hasn't changed.