I dont think there are holes in the balls. I've seen a throwbot demonstration on TV a long time ago when it was first introduced on some PBA show and they positioned the ball in there with an imaginary set of lines on it for the grip, program the tilt, rotation, speed, and revrate. Throwbot then brings up the ball to the peak of the backswing and it starts spinning in the cradle, then it comes down and releases the ball with the indicated specs.
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-DP3