The quickest and simplest way of separating a collection of balls you're happy with is to sand the biggest hooker, and polish the smallest.
When you say that they have the same reaction, do you mean shape/length/overall hook?
It also depends on what pattern you're bowling on. On many THSs the pattern dominant and it largely doesn't matter what you're bowling with, there's only one place to score from.
Bear in mine that sanding will make a ball hook earlier and so will change the reaction shape making more of an arc. Whilst polishing will make the ball go longer, hook less, and be more angular at the breakpoint.
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Reporting from England
