Jax,

I'm not sure I understand what you're saying?

On my Boom, With a free footed main, I have no upward pressure other
than at the Clew of the sail and at the Tack. I believe this to be about
the same with a boltroped foot also. Pretty much so.

My downward pressure is supplied at the center location by the center
located main ( three blocks) and the vang appox. 1/4 of the way back
from the Tack. This is transmitted to the clew and the tack of the main
by the Boom

I have no direct effect on the center effort of the sail by downward
force of the boom. This downward pressure controls the twist of the Main
( Leech Tension)

I'm not sure what you are saying about center of effort, Am I missing
something?

Ole Thom