I am having problems with my thumb. I currently am having problems with developing blisters on the nail side of my thumb slightly above the joint on the right side of my thumb. I am right handed. The ball is drilled with 1/4 reverse on the thumb and fingers I believe not much bevel on the thumb hole. I can feel the ball drag across that area as I start my down swing and again just as I release the ball. I have never had this problem before but this is the first I have had drilled with the reverse pitches. Some people have told me I am gripping the ball with my thumb and that is what is causing this but I haven't had this problem before. I was wondering if Gizmo or Just Rico or anybody else who is knowledgeable could give me any incites into if this is a grip problem or a me problem.

I second this.  I'm guessing the same.  If it's the first time you've gone with the reverse pitches, I'd suggest getting rid of it in the thumb, but keeping it in the fingers and trying that.  Also definitely check your span.  If your span is too long, it will put your thumb specifically out of position.  While relaxed, your thumb socket should be directly above your thumbhole.  If you have to stretch at all to get it there, it's too long. 

What is your span?

Span will dictate pitches more than any one thing.  My initial guess is way too much reverse (unless your span is quite long). 

You're probably putting the "death grip" on the ball trying not to lose it, but according to you, it's still slipping. 

As an example, my span is around 4 1/2" and over the years I have gone from 3/16" reverse on the thumb to 1/8" forward, and I now use waaaaay less grip pressure than I used to.  The only way you'll really know is to start tweaking pitches a little at a time until you feel right.  All of our hands are different.

Thanks guys I had him check the span and it was okay. I was actually even more reverse than I thought on the thumb 3/16. we changed it to 1/16 reverse and that still didn't fix the problem so we took it to 1/16 forward and I think it is doing a lot better now.

Wow. That's 1/2 inch total change. Quite a bit in my opinion. How long did it take for you to adjust? Did you compensate any with bevel?

1/2 inch?

A quick way to check your span, "for a finger tip grip", is to insert your thumb all the way into the thumb hole and extend your fingers flat on the ball over the finger holes. The first joint of your fingers should extend pass the finger holes about 1/4" of an inch.
This is comfortable for most bowlers, but personal preference can and do vary.