hosee - watch the polarity...
"Sounds" like a whopper of a system. I am dreaming...
But, it looks like you have a phasing problem in your fronts - between the 4312's (positive) and the custom cabinet with the 2202H woofer (negative).
If the 4312's are factory, and the 2202H is hooked red-to-red, JBL designed that 2202H trasducer negative, meaning cone excursion is "in" on positive signal - so it is 180-degrees out of phase with the 4312's. If true, you're missing a great deal of bass response, and imaging. But, with your obvious experience, maybe you knew this already.
I don't know the L166's (by vintage they may be positive) or the L500's - somebody else out here might. Also, make sure your mid range compression driver IS out-of-phase with the woofer and tweeter - it will improve imagining.
I am suspicious on the 4350's - they are likely negative. Most of the upper end 43-series were negative it seems. I had paired some 4312's with some 4313's, and had to cross-wire the components in 4313 cabinet - the improvement was astonishing.
I (re)started a Thread on this under "Technical Help" - since the prior discussion went down with the old Forum.
Id' love to know what you find, and what you hear...