I also think that laying a weightblock(think a rolling pin for conceptual purposes).  Creates a dramatically different reaction than having a rolling pin straight up spinning end over end.

This image comes from Revolutions 2 by Chip Zielke.

A rolling pin laid almost on it's side say a 3 X 1 drilling is going to roll easily but is going to remove much of the potential for the core to fall hard or flip at the back.  Versus the same ball drilled 3 3/4 X 3 3/4 is going to roll a little later(higher rg drilling) and then have a tremendous amount of potential to fall or flip as the ball loses speed at the break point.

The arcy drilling with cg out and rolling pin on its side is great when one wants to avoid getting high on the head pin.  The flippy drilling(stacked or vertical rolling pin) will bring and assist one in getting higher on the head pin.

Weightholes will fine tune even more, either enhancing smoothness if on the PAP, or imbalance and reaction past the PAP which also preserves most of the top weight.  Or even angled to the bottom of the ball maybe adding top weight.

REgards,

Luckylefty

PS I've seen very similar reactions from 2 X 4 1/2  drillings with no weighthole and 4 X 2 drillings with weighthole on PAP.