Closer than leverage to your pap is going to reduce flare and get the ball to roll sooner and be smoother on symmetrical balls. I've had success with several balls that I put anywhere from 1 to 2.5 inch pin to pap on. Most recently, on a Grip It. I think I chose the wrong ball, because it's super early and smooth. I did have success with it on a Predator and Track Money.

Now, for a switch grip, any top should do, since you're going to be taking out more of the tw with the hole.

No. If you have 3 oz of top, you're probably not going to end up with bottom. Depends on the size of the holes you're drilling, but unless you're drilling a ball with either 5 oz of top or 0 top, you will be within static limitations.

Oh, my bad. Shorter pin lengths (from CG) limit layout options, so you may not be able to tweak the cg to be able to add an extra hole. Also, they say pin ins have less flare potential. But if it's over 1.5, I think it's considered a pin out. I don't remember specifics.