Hitting up on a ball is never a good basis for a consitent ball reaction, so this might be the primary source for over/under reactions.
Nevertheless, I'd suggest taking the polish off of the ball. Even though PK 18 reads the lane well and early, the polish basically sharpens the reaction between oiled and non-oiled lane areas, generally on any ball.
Once the ball hits dry, it goes off, and if you have a good am,ount of oil on the THS, the reaction at the "rim" between these areas can be dramatic. If there is much oil, carrydown might also be an issue on later games.
A ball with an "open" surface will react less itchy. If you use a very high grit (e. g. 2.000 grit), you will not sacrifice much length. But the ball's reaction at the breakpoint might become more stable and easier to control - as long as the release is consistent.
It is IMHO worth a try, and if it does not work, you still can the ball back to OOB condition easily with some polish, or try a slightly coarser finish to see what happens (some trial and error might be necessary).
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DizzyFugu - Reporting from Germany
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