Heels on the bar at frontend, release to heel hang
Swing out from the platform. At the frontend, bring the legs up in front and hook your heels onto the bar with your butt up close to the bar. At the backend, put your head back. Just before the peak at the frontend, let go of your hands and hang down from your feet for a split second before making the catch.
You can find out more about this trick in following books: