So your driller installs a Turbo or Vice Screw in thumb slugfor you. You remove the slug from the ball and have it on your thumb....

If it spins all the way around your thumb, is this a good fit or bad fit?

Vise versa, if it will not turn around your whole thumb, good fit or bad fit?

I feel the one I have had done are to round for me, but wanted to hear what other thought about how a fit should be.

Also, I have the IT slugs and I have one more question. I can actually click the bottom of the slug with the nail from my thumb....I have a short thumb too! It really hasn't bother me to much as I have tape over the nail, but I have never had a ball were my thumb "bottomed out". Did he just use the wrong length slug or not drill deep enough? The slug is 2 5/8's from the bottom of it to the highest point on the top.

Thanks BG

If it spins around your thumb it doesn't fit your thumb properly. It sounds like your thumb is oval shaped, like many of ours, so your driller should drill your thumb hole to match.
Also, your thumb hitting the bottom is also less than ideal.

Maybe the driller expects you to use some tape. My thumb hole alone does not fit, but once I apply the proper amount of tape, I can get exactly the correct fit. Your thumb will change  depending on the day and as you bowl, so you do not want a thumb hole that fits perfectly without any tape in my opinion.

There is no way anyone here can critique a fit by the description you provided.  What you are saying is that your driller simply made a round hole....which isn't "wrong" for any bowler.

Even if it is a bit loose....if it works for you then it's right.  There are some bowlers that prefer a loose fitting hole to pile tape in (like me), and there are others who don't like to use tape and want it to fit like a glove.  Neither is wrong....

Your thumb is bottoming out because the slug hole was not drilled deep enough. He should be able to take a slightly smaller bit and take a little out of the bottom of the hole to solve this for you.

If after applying the tape you wear and taping the hole using a reasonable amount of tape, the hole is too lose, causing you to grab or loose the ball, I would say plug it and redrill it smaller.

Before going to switch grips, I was more concerned about my thumb holes being the same size from ball to ball. I used tape on my thumb to take up slack because it was difficult for me to duplicate tape application from hole to hole.