You must forget about the Clubshaft Plane. If for no other reason, the Clubshaft simply cannot stay on it.
As the Sweetspot moves Up, Back and In On Plane, the Shaft rotates off its own Plane and onto the Sweetspot's Plane. For Swingers, that Rotation is accomplished during the Start Up Swivel. The Clubshaft then remains on the Sweetspot Plane during the remainder of the Backstroke and also into the Downstroke until the Release Swivel once again rotates the Shaft around the Sweetspot and back onto its own Plane. For Hitters, that Rotation is gradual on the Backstroke -- the Pivot and Arm Swing bring the Left Wrist and its Angled Hinge Action into an On Plane alignment at the Top -- and the Downstroke Rotation mirrors that of the Backstroke.
The Shaft and Sweet Spot remain on their respective Planes during the Hinge Action (until the end of the Follow-Through, i.e., the Both Arms Straight position). Then, the Finish Swivel -- for both Swingers and Hitters -- rotates the Shaft once again onto the Sweetspot Plane for the Finish.
So, forget about the Shaft Plane.
Point the Sweetspot.
Or, in drill, point the Dowel's end because it is the Sweetspot substitute.
Best of all, learn to Feel the Lag Pressure (of the trailing Sweetspot) and Trace with it using your Right Forearm and #3 Pressure Point while keeping your Left Wrist Flat though Impact.
This is the essence of The Golfing Machine®.
I don't believe I have seen this description but, my search skills seem to be lacking. As always another educational experience!
I can and want to experience/feel the shaft for the preselected Downstroke Clubshaft Plane (10-13-D);the Wedges (6-B-3-0-1);The Basic Strokes (7-3); and the hands down the inclined plane (7-23). However, from release into impact there is no clubhead feel with the dowel. Maybe I am expecting too much from the dowel drill.