PSA is the preferred axis the ball wants to roll on and will try to migrate to while rolling. This moves slightly after drilling as you have reshaped the core and changed the dynamics somewhat.
Some balls have a PSA some do not. Those that do, have varying strengths of PSA (ie their spin times to reach their PSA.)
Statics have very little or no impact on reaction.(lets not start another runaway thread on this!)
Puttin the CG in the thumb will have very little impact other than needing to drill your thumb deep to maintain static legality. The pin/core location is more important to track flare/migration.
PSA is not a positive/negative side thing its the plane that the core wants to
spin on as being its most stable axes.
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Billy Ray
Edited on 6/24/2005 7:54 AM