before I would blam beveling I would look at the span. over beveling a hole to clear a thumb or releave presuure can cause you to grip the ball to stay on your hand. forget about a free swing at that point. over beveling changes the span so that the base of the thumb is closer to the fingers. that is span change but done the wrnog way.
proper fitting should provide a harmony with your hand that ioncludes spans,pitches,hole shape( oval, round) and bevels. inless dictated my some hand anomaly bevels shoud be to knock off corners and that is it. lot's of beveling = bad fitting.
FWIW. I don't even bevel the hole and have soft pillow like office hands. I can hook the lane if I all day and no problems.
it did take me years to get the right drilling so seek out some qualified drillers. grab a few cheep balls from here and hit 3 or 4 pro shops that you hear are good around your area. it's worth it. I now have a driller that I can fly accross country ahve him drill me a ball and ship it. and just hity the lanes with it.
a 15/16 ball hanging off the end of your hand is not natural. seek out way to get that ball fitted as best as you can to provide the most comfort as you can. unless you are feeding a family with your game do not go against your natural ergonomics to gain 2 revs. you will bowl better in the long run.
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It was a fine time for me - I was learning to fence, fight, anything anyone would teach me