I have spent time reviewing your findings in the past but have read it as an overview because of my lack of understanding. Last night, I spent more time with each link bullet point feel I'm getting a better grasp on your work in this area. I'm finding it helpful to jumping back and forth while reading it to better clarify terminology, theory and supporting data. It's starting to come together for me but it's a slow process for a rookie like myself
What I will say is this, in following your lead with the two implementations of your 4Pi design I have completed have produced wonderful results.
Following the formula of another now popular 2-way design has produced a "ambitious" speaker but a bit of a swing and miss in comparison. To be fair, some of this is probably due to the more economy minded compression driver used.
I have organized much of the link info and commentary now and will be printing it out for some more formal reading time.