After an initial drilling. What prompts you to add an x-hole? What motion or lack there of warrants this decision?

After an initial drilling. What prompts you to add an x-hole?

Well either to make the static weights legal or because there's a lack of motion or too much.

What motion or lack there of warrants this decision?

What warrants the decision?

Well if you think the ball motiopn is too strong looking, you decide whether to add a hole to reduce differentials and cut down on its track flare.

If the ball motion is too weak looking, you decide whether you want to add a hole to increase the differentials and its track flare

And if the static weights are too much you add one to lower them.

In a couple instances where I drilled a ball that was too squirty, or quick to transition, and left all kinds of flat 10's, 4 pins and solid 9's I use a hole to slow the transition from hook to roll. Technically  I am strengthening the ball by raising the diff which widens the flare. This helps me read the shape of the ball on  the lane easier, and I don't have to be so perfect with speed and angles when the ball is overly sensitive to what the lane pattern is giving me.

In a couple instances where I drilled a ball that was too squirty, or quick to transition, and left all kinds of flat 10's, 4 pins and solid 9's I use a hole to slow the transition from hook to roll. Technically  I am strengthening the ball by raising the diff which widens the flare. This helps me read the shape of the ball on  the lane easier, and I don't have to be so perfect with speed and angles when the ball is overly sensitive to what the lane pattern is giving me.

I think this explains it very accurately. I had a Hammer Toxic which was just a meh ball overall. Nothing special! I added a double-thumb weight hole and this ball turned into a med-heavy oil killer on a fresh shot!!

I have an LT-48 with a lower weight hole, smaller, but similarly placed as the one on my Toxic. I couldn't use it, because my speed and rev rate didn't match with the ball's transition on the backend. When using this ball on medium oil, I would ping ten pin after tenpin!! So I plugged it and moved the weight hole higher to slow the transition, and now have a versatile, and very useable piece!