[HungryBear]

I think the swing left deal equals on plane. To keep the sweet spot on plane the feeling would be swing left to players that swing right. The only way to really understand the plane is do what Homer did. Build a plane board.

I have built both a plane board and a PVC plane rail.
The board is simple. A 4x8 sheet 1/2" covered foam insulation. Cut a 30" radius center-edge. Adjust with 2 48" driveway markers for angle desired. < $7 cost.
Rail is 2 10' lengths 2" pvc (grey) electrical conduit, 2ea. 2" PVC (white) DWV (pluming-drain) "T's" and 90*'s . cut one 10' into stand pieces and cut molded coupling off one 10' to fit fittings. No glue, friction fit, assemble when using. $10-$12 cost.
Good and Bad points.
Good- gives a clearand different view of swing
Bad- Both promote a tendency to try for a sweep release so the shaft rides on the plane. You have to overcome this tendency or U are doing nothing.
ALSO- ( I do things on the EDGE so these are my "damages") I have nicked the plane board low/right between release and impact- only during swinging [only use Irons]. I think this is hossel hitting board at swivel because sweet spot trys to stay on plane so hossel goes underplane.
I quickly smashed the rail and had to replace because after a few swings I tried a metal wood. The good thing was I hit the bar less than a club length behind the ball . SO remember a metal wood has a big protrusion below plane before swivel. Irons don't do this so not an off plane movement.

The Bear