For what it's worth. I'm basically a beginner myself. Just getting back In The course after 5 years away. I can run -15 34mph with out any troubles. But my technique is still horrible. When I went to 22 off I suddenly had slack line and could barely get 2 balls. I had a friend take a few videos. Went home studied BOS until my eyes bled and figured out I was not getting wide enough for the gates, I was pulling way too long (past 2nd wake even), and my body position was wrong at every point. Went back out and worked on the those 3 things. First was to develop my stack. A few sets later, body position is much better, which created more angle and speed into the wakes. The edge change is happening sooner and effortlessly, and we're carrying more speed into the next ball with a tight rope. Now I'm skiing -22 successfully. I am not aware of doing any of the above mentioned "moves" to edge change. For me it feels like it just happens, especially when I've done everything else correctly.