I thought I read somewhere once that there was no minimum, that's what I was going off of. I guess where ever I read it was wrong as I see there is a minimum.

Also, I believe a smaller ball can rev up faster. Where is our local physics teacher?????

Lol, the only thing that came to my mind when thinking of a smaller ball, is less pin action. It probably wouldn't make that much of a difference but it can always mean just that little bit of even a few cm.