Thanks @poseidonsvoice. Those bass integration articles were really informative. I'm a touch limited as my subs are attached to the mains, so every positioning change I make in either influences the other. Still have the controls of cutoff frequency, phase and gain on the each of the sub amps independent of the mains was the ticket. And then also being able to treat the axial mode actively with the black hole generator was helpful.
Sound-wise, it is definitely an improvement. Bass is tighter and not as peaky. Imaging/spatial separation is better. I'm getting a more stable center image as well.