@@MrPottsTeaching Actually the "vent hole" is only for installing the slug as it does not connect in any way to the thumb hole. The vents sole purpose is to prevent trapped air between the ball and the slug. If you look at a slug before installing you'll see the groove runs the full length of the slug and has no holes that intersect with the undrilled area for the themb hole.
From my slight experience with a new ball, if you have a death grip, it will widen your thumb and cause it to catch. As I understand it one of the reasons that tape inside the thumb hole helps is that you have better confidence in your grip and therefore can lighten up a bit...
