I have practiced the "impossible (not) turn" and taught it in at least two different aircraft types. I was not prepared for how the FX-3 behaves. I needed 500 ft to make it back to the runway with an idle cut at Vy with flaps 1. I worked up from 300 ft from which I would have crashed off airport. It takes less than 300 ft in my PA-28.
If you try this I suggest starting at least 600 ft agl. You will be surprised at the altitude lost. Practice high up first and be sure you can keep the ball centered.
If anyone can do it consistently from less than 500 ft please share your technique.