There are no hard and fast rules to it. The idea is just to look at your current arsenal, and find out which type(s) of lane conditions
are not tackled. The next ball should fill those gaps. Then when it comes to picking a ball, simply pick one that is suitable for that condition. Here's an example:
You have a ball for blocked lanes and medium/short oil patterns, but none for floods (wet) or toasted (dry) lanes. So you have two voids to fill. Which are you more likely to encounter? Let's say you decide on a ball for drier conditions.
Thus your next ball should be one that is generally meant for that lane condition. For instance, with high RG (more length), low differential (tame backend reaction), and mild coverstock (to conserve energy,
as opposed to low RG, high diff., and an aggressive shell.
Based on this, the appropriate layout is selected - if you don't know, your driller should. A good one, anyway.
That's how I select a ball. I'm don't think there are "balls for certain types of bowlers only". All one has to do is to match the proper ball to the conditions one is up against.
P1
Don't take to heart what was said of your shockzone. There's no such thing as a layout that won't work. If that were the case, why do spinners bother to drill balls designed for heavy ball bowlers?
There's always a condition out there for your ball. I have a chaos (heavy, heavy oil ball) drilled with a 7" pin position with negative side weight and a heavily shined cover and I use it as my control ball on clean backends. I can carry well on those contitions, but not much else - but that was not what the ball was drilled for, was it?
Drilling is simply a way of tapping the potential of a ball. Whether or not that potential is reached is also a factor of lane condition matchup.
Finally, my personal opinion is that a stronger layout on a weaker ball would seem to bring out more potential than a weaker layout on an aggressive ball. But it's always a balance with certain trade-offs. I have a lot of strong balls with weak layouts because I desire the stronger cores of these performance balls. If I got weaker balls with stronger drillings, their weaker cores would mean that on most conditions, I would have to create angle to the pocket to carry a strike. Thus, I prefer to play tighter lines with control than a wide hook in order to obtain carry.
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