Jock posted this once, and I kept it for reference.

http://www.jayhawkbowling.com/Pro_s_Corner/Fitting_Tips/fitting.html

It looks like you may have too much right pitch and or too long of a span.

You can tell if your span is correct by placing your thumb in the ball and laying your fingers across the holes. The leading edge (side closest to the thumb) of the finger hole should be no longer than half way between the first and second knuckle of the middle and ring finger without stretching your hand, it should be relaxed. It can be a little shorter than that, but not shorter than one quarter from the second knuckle.

Another way of determining if your span is too long is to put your hand in the ball and see if your fingernails are pressing the back of the holes, if that is the case your span is either too long or you may have too much forward pitch in the fingers.

Sorry to hijack this thread, but i seem to be having the same symptoms as Juyce. The inner joint of my thumb(as seen in Juyce's pic) are feeling painful after every bowling session. The skin is getting thick in that area.
I've checked my span and it does seem to be correct. The leading edge is between my 1st and second knuckles. What else might cause the same problem?