I have a great deal of experience flying in max-effort rudder-on-the-stop slips in numerous aircraft ranging from Open Jantars to K-21’s to the awesome AS-W12 and have never felt the aircraft uncontrollable. Have flown literally hundreds of patterns in full rudder-stalled slips right through the flair as this is the only way to land a -12 without using the drag chutes. Never saw a problem.