[Jeff]

Toolish

I presume that we agree that the clubhead never travels in a straight line and that its path is always circular.

Here is a tracing of Kevin Na's clubhead arc through the impact zone.



Although the clubhead arc is circular as the golfer traces a SPL, the clubshaft lies against the surface of the inclined plane as it travels through the impact zone - as seen from a DTL view. In that sense, the clubshaft must stay on-plane against the surface of the selected inclined plane (eg. elbow plane) during its passage through the impact zone.

Jeff.