Extensor Action is Below Plane through-out the Stroke.
#1 Accumulator is On-Plane.
What Alignment is needed to allow this?
Both use Triceps Muscle but only when the Flying Wedges are Aligned at 90 degrees can you have both Actions. I think this is an important point.
The 90 degree Wedge Alignment allows the Right Forearm Wedge to remain at Right Angles to the Left Arm Plane while the Clubshaft is On-Plane. The Clubshaft is on Both Planes Simultaneously.
This needs the the "Inside" of the Right Wrist to be visible (Facing you) through-out the the Swing from the End of Start-up to Follow-through.
Most Pros include this Alignment from the Top and during the Downstroke but HK uses the Right Forearm Take-away so the Alignment is available in Both Directions.