I have been working a lot lately for below plane issue. With the right forearm tracing, it solved.
Cup left wrist at the top issue and across the line, solved with taking the grip at low point instead of mid-hands position.
With video recorded, I saw a swaying machine however, approaching to the top of the backswing, my upper body will trend to lean forward a bit. My head is directly above the ball instead of slight behind it.
I have my axis tilt at setup, I knew that my right shoulder need to be down plane with hip slide for the start down. With most of my effort made, the upper body with my head still sway forward….
Any drill to rectify this?
__________________
If you cannot take the shoulder down the clubshaft plane, you must take along some other path and add compensations - now, instead of one motion to remember, you wind up with at least two!