At release, it is where the fingers are, in regards to the thumb, in reference to a line perpendicular to the foul line, that create PAP coordinates.
If the fingers and thumb are in line, there will be very little if any, vertical coordinate. The longer the thumb stays in the balls, as the fingers rotate around this line, the more the vertical will go up. Also, if the fingers are on the outside of this line at release, this will cause a lower lateral, as well as higher vertical.
When the fingers are more on the inside of the line, generally the thumb will be on the outside, which can create an earlier release and a lower vertical coordinate or an inverted track.
Hope this makes sense.
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Formerly BrunsRico