I have several balls drilled for full roller both assym.& sym. and they both work great for me.
1.7:30 pin location best suited for balls that arc
2.1:30 pin location which causes the ball to flare in reverse best for skid/flip reaction.
So i think that what ever core you choose to drill it still depends on the reaction that the ball was designed to do and the type of reaction you are looking for.These 2 drill patterns have given me possibilities i didn't think were possible "IMHO".
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A Bowling Ball A Day Keeps The Doctor Away