I've tried to tailor the laterals to the person's fingers, arthritis is very unpredictable. Make those pitches go in the direction of the crooked fingers.
Have drilled as much as 1 1/4 reverse for guys fingers, he was about 30 years old and his fingers were this stiff. Makes gluing in grips a little tough, but can be done, and he said he could bowl without pain.
Don't be afraid to try some different things, nothing is wrong if it works.
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