Doug, I guess I'm missing something..
Yes, any drill that put the cg and pin equidistant from the PAP would then fall into this category. No doubt. Like:
3-3/8 X 3-3/8
4 X 4
5 X 5
However, these layouts will give different reactions for sure also.
I have to agree with tenpinspro that overall hook and carry will vary according to the style, ball's specs and lane condition.. Therefore, in my humble opinion, stacked drillings will not always give the optimum reaction desired. Honestly, I respect your posts here and read them with great interest. But, I'm really confused here regarding what you really would like to ask..
Regards,
Burak