I recently got the turbo switch grips installed into my bowling balls and got my pitch changed to 3/8 forward and 0 lateral. I am not squeezing the ball anymore after adding the forward pitch but I am starting to get a blister on the left side of my thumb (if you are looking down at the nail). Is there anyway that the driller can change the lateral pitch by just doing a new slug? or would he have to put new sleeves in all of the balls?

Maybe I'm wrong but I think only minimal, if any, pitches can be added to the slug itself. Maybe 1/8. Other than that a plug and re-drill might be necessary.

Show your driller where your thumb is rubbing and let them determine how it needs to be adjusted. As Jay said they can make adjustments as much as 1/8" without plugging A lateral adjustment would only be 1/8", so I think you will be fine.

That's what my driller told me also, for IT.

Perhaps when one switches to a new type of thumb hole, it would be best to hand the driller a ball and say "duplicate this". Then throw the old ball and the new ball side by side until you're satisfied that the drilling worked as planned. Only then, go ahead and drill the rest of your balls. That's what I did, and I was satisfied with the results.