So, I decided to try the Ultimate thumb process from Buddies. I sent them my ball, a Cell that has been absolute $$ for me, and in about a week I get my ball back with my new thumb slugs.
Now, here was my issue. The ball I sent them was in great shape. The ball I got back appeared to be bounced off the conrete several times. It's basically destroyed. My guess is that UPS dropped it a few times, but who knows. So, I call them up, explain what happened and email them some pics of the ball. Literally within 5 minutes of sending the pictures I get a call back. They offered to re-surface the ball for me or send me a new one.
All I'll say that as far as on-line proshops you can not beat Buddies! Their service is un-surpassed. Oh, and as far as the thumb slugs - PERFECT fit!