There are a couple things you can think about to fix an "over plane" right shoulder startdown.
Turn your right shoulder to the inside aft (rear) quadrant of the ball.
Take your PP3 (right forefinger) to the inside aft quadrant of the ball
Work on downstroke waggles - from the top, look and feel the correct motion of an on-plane right shoulder startdown. Go slow, and move back and forth between a Top position and halfway down. It's simply rehearsing that first move down to get it into your Computer.
This should give you a completely different startdown feeling than you've been having. The right shoulder needs to go not ONLY down and not ONLY out, but instead both at the same time to keep the shoulder on-plane.
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