That "1 inch from any drilled holes" rule is pretty standard throughout the industry, and I would suspect it is the same with C300.
That being said, I have had decent luck getting a ball replaced that had stress fractures around the fingers, AS LONG AS IT DIDN'T INVOLVE THE PIN in any way.
If the crack came from the pin, or was caused by the pin/hole location proximity, you may have a tough time.
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"The difference between stupidity and genius is that genius has its limits."
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