Gripping, grabbing, squeezing... Whatever word choice you want to use, I was bending my thumb in the hole. This created an endless cycle of the ball sticking to my thumb, and me needing to insert a larger thumb slug, resulting in my bending my thumb a little more. And I like my thumb holes to be slick rather than rough because of my hands sweating so much, so I needed the white tape to allow my thumb to grip the slug. Between keeping my thumb relaxed and the weather being cold, I am currently down to my smallest insert and blowing in the thumb hole every few shots.