PSA is an axis, a line through the spheroid we know as the ball. One end is usually what is colloquially called the Mass Bias. I have not seen any proper name for the other end. Since there is a Positive Axis Point and a Negative Axis Point, I guess if one end of the PSA is the MB, the other end of it might be termed the Negative mass bias, weight removed from the other side of the core.
A ball with a high enough (how high is still open for debate; minimum is considered to be .008 by Mo Pinel) mass bias differential will want to spin on its preferred spin axis, of which the Mass Bias is one end, usually placed with reference to the Thumb or X" away from the bowler's PAP. The Mass Bias of these balls remains fixed with the PSA (I believe) even after drilling; that is a feature of Asymmetric cores with a strong enough MB. Symmetric cores have their PSA generally stick near the thumb.
I think that's close enough. Experts, please feel free to correct my memory; ain't what it used to was.
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Bowling: Just like hand grenades and horse shoes, you only have to get close.
Life: Deal with what is.
