when i first got my power groove i thought i was going to use it for spares ,it quickly changed my mind. I have noticed something here of late that seems to work a good deal of the time. Whatever ball i am striking with I shoot my spares with. I have been driving passed the ten pin when i switched to a weaker ball because of the oil in the middle of the lane. Unless the backends are fried my strike ball is the best ball to run the rail at the ten pin,everything else you have a read on the lanes with the ball u are using to strike with so an aadjustment here or there and the rest should fall into place.
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my style, the art of bowling without bowling