John
The pin is migrating towards a stable position. At some point it will reach if it is allowed to, depending on speed and rev rate. The distance between the pin and the PAP narrows as it travels down the lane.
If you notice when you place weight holes down the VAL, that eventually that hole becomes the PAP as it is traveling down the lane, usually around the midlane. This allows the ball to respond to the midlanes better.
Generally the path the axis follows, depending on pin height is going to be towards the gripping holes. If the pin is down, the path migrates towards the thumb. If the pin is up, it generally migrates towards the center of the holes or the ring finger.
Hopefully this is making sense...
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Formerly BrunsRico