We've been utilizing the reverse finger / forward thump pitch move on a good number of the more competitive bowlers in our area lately with great results. I was personally on a new grip quest for some time and tried a CLT, various pitches, spans, etc. I have recently settled on a grip and have even molded my thumb to insure an exact feel from ball to ball.
My span only change by 1/16" on my middle finger, but my pitches change a whole lot:
Middle: OLD - 1/4 For x 3/8 L to NEW - 1/4 Rev x 1/2 L
Ring: OLD - 1/8 For x 5/16 R to NEW - 3/8 Rev x 1/4 R
Thumb: OLD - 3/8 Rev x 0 to NEW - 1/8 Rev x 0
A whole bunch of changes, but as a result I now have a more relaxed feel in the ball, don't have to squeeze as much, have a free'r release and don't hit the ball so darn much anymore. The new pitches and span also have allowed me to tilt the ball more which produce better projection down the lane.
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-Chris: DJ's Pro Shop : Auburn, MA