It's a good short read that explains a lot of useful concepts used in the constant directivity cornerhorns, matched-directivity two ways, multisubs and flanking subs.
I have read your white paper before; it's a great read, and certainly worth looking at again.
Do I understand that the main advantage of the upgraded woofer path for both the three and four Pi are the copper shorting rings the Eminence drivers lack? And therefore the improvement in the upper range of the woofer response is significant?