It's the plane on which the path of the sweetspot moves and you learn to monitor it precisely by practicing driving PP#3 at the required Aiming Point for your Swing with the PIVOT.
Pardon my French; HORSEFEATHERS; I can blindfold U and put a club in your grip and you can't locate the "sweetspot" or "sweetspotplane" without grounding the club or loosening your grip. Never by swinging on any flat plane. Period.
Threaded Mode
