Extensor Action is a Non-Accelerating Thrust. Use as much as you can. Although it doesn't Accelerate the Clubhead directly, it contributes to precision of the Accumulators.
Quote:
Clubhead Lag (7-19) promotes even and steady acceleration, assuring dependable control of distance. The Power Package utilizes four types of Thrust:
Accelerating (Accumulators driving the Lever Assemblies)
Non-Accelerating (Extensor Action supplying Power Package Mass)
Acceleration Control (Lag Pressure Point sensing Clubhead Inertia)
“Centrifugal Acceleration” (Centrifugal Force pulling the Clubhead toward its In- Line condition)