I can only think of one word in response...WOW
Now that I've seen (and heard) what one 15 inch sub will do, I can't imagine the pressure wave from an array of six.
I hope you carry earthquake insurance and that your home is built to handle the vibrations. Be prepared to have to find and silence a few rattles... in your neighbor's house...
I say, go for it... It is only sawdust (and $450.00 in drivers) You do realize that with the much longer wavelengths involved, you can space the drivers a bit further apart before having to worry about comb effects.
Some day, I'd love to hear it. What state do you live in?
Your PDF is great. Be aware that there are two errors in the plans on the Audax web-site.
The woofer crossover schematic for the Center channel has the woofer polarities wrong. The pictorial illustration and the description in the text both (correctly) say that the woofers are wired "out-of-phase" The schematic incorrectly shows the minus input lead connected to the minus terminal on the woofer. That should be the plus terminal.
Basically, the polarity of both woofers on the center channel woofer crossover schematic is opposite of what it should be. The pictorial illustration of how the woofer crossover is physically constructed is correct. E-mail correspondence I had with the designer, Joe D'Appolito, confirmed this.
A second error: The pictorial illustration of the woofer crossover for the left/right front speakers is incorrect, there is no wire connecting the midpoint of the two resistors (R2 and R3) connected in parallel with the woofers and the junction of L2 and C1. In this case, the schematic drawing is correct.
I did not run into these errors as my crossovers were wired by Madisound and supplied already constructed. Since you have put together the PDF, you might want to add a note describing the errors in the drawings.
By all means, feel free to ask questions as you proceed on you project. Thanks for the PDF.