I'm sure Don could work out the math on what minor MOI changes my style creates between different guns. I'm ahead of the teeter point, and the CG is typically between my hands.
I never feel the mass in my left hand when I shoot.
Craigd, essentially, I put the button of an Anson pushrod right in the crook of my index finger on every one of my SxS's. If no push rod, the forend tip. So, my left arm is well extended.

For the same distance between forend tip and stock butt, it's a very reproducible hold.
I'm not smart enough to move my leading hand back for more barrel speed on a long crosser. I have to just pull/push harder.

And because I shoot a ton, I know what a killing shot typically looks like as soon as I start my mount.

Out there doing it best I can.