how much difference in reaction can you expect if u shorten your span ,and what is the proper feel,setup for a fingertip drilled ball. i was bowling yesterday and noticed that with a longer spanned grip i was able to deliver the ball with more velocity than with the shorter span. I had my span shorten on the advice of a local used to be pro,but every since i shortened it my speed and delivery has realy been labored and slow maybe i just answered my own question ,but i would really like some informed advice.
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my style, the art of bowling without bowling

Why would shortening a span have anything to do with ball speed?

Ball speed comes from your foot speed combined with your arm speed.

The only thing I can think of would be if you now have too much reverse for your span and you are having to grip the ball to hang onto it. The gripping action could cause muscling of your arm swing plus if you feel you are going to loose the ball it might shorten your backswing as well in an effort to hang on.

If the above is true you should look to move your thumb pitch in the direction of forward.

I’m a firm believer in relaxed finger tip spans. I believe it gives the most versatility and comfort available.