The reason is because plastic and clear balls do not have the same covers as reagular reactive balls. Plastic will hook a little bit if you have enough hand and the lanes are dry enough. We saw this with the plastic ball tournament where they only could use plastic and the pattern was short with half the normal volume. You could easily take a White Dot or whatever and sand it to 1000 and get it to roll a little. But a pin axis drilling will give a good coverstock to start with and you wont need as much surface. Plus with a plastic ball the hook will still tend to be on the backend, not exactly what you want when you are a high rev player trying to go up the boards. Pin axis gets the ball rolling the whole way down the lane but it is very gradual....
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HAMMERDOWN!!!