[Daryl]

Do I interpret On Plane force to mean my right elbow is on the plane so that the unfolding produces the On Plane force?

The #3 Pressure Point Thrusts against the Center of Gravity (Sweetspot) of the Clubhead. So, the #3 PP and the Clubhead Sweetspot are always On-Plane.

The Elbow is not on the Sweetspot Plane (Swing-Plane) until Impact unless the #3 PP and Clubhead Sweetspot are on the Elbow Plane. Using the Elbow Plane as your Swing-Plane, then the Elbow will arrive On-Plane at Release. Then, your Right Forearm, Right Elbow, #3 PP and Sweetspot of the Clubhead all travel the Plane from Release through the Impact Interval. The Elbow is not On-Plane from Ball Separation to Both Arms Straight.

With the TSP, the Right Elbow becomes On-Plane (on the Sweetspot Plane) at Impact and can remain On-Plane till Both Arms Straight in the Follow-through.