Just to recap, I'm looking to have the bass that would normally go to my subwoofer simply play through my huge main left and right speakers.
Setting the fronts to "large" and the sub to "none" will accomplish exactly that.
I'm also in the dark about what "Sm Speaker Bass" means when looking at the bass management matrix page.
That means that the subwoofer is getting bass redirected from speakers that are set to "small" - with the bass determined by the crossover point(s) set for those small speakers.