I built the 4pi Pro many years back. Best speaker I ever heard and had. Now they serve as front speakers in a serious home theatre setup.
From the FAQ I gather that I need to build another pi4 (eminence drivers) for the center-speaker to make this sound right. The speaker will live behind the screen which is about about 3.5 metres wide. If this is correct, plans please I fear over the years I lost the previous email (15 years..). Can I do away with the porting for the center? would make the building process easier?
Subwoofers needed as well, I gather 2 "small" 3pi subs are better than once 12pi sub for this purpose? the requirements are 20Hz properly audible, i.e earth shattering when required.
I'd go with a center four Pi to match the right and left mains. You can delete the port on a center channel four Pi speaker, just center the tweeter. Use three Pi subs flanking each of the mains, and if you have room on the opposite side of the room, add one or two more there for modal smoothing.
One last thing - if it has been 15 years - you probably want to upgrade the waveguides in the left and right mains. It's an inexpensive upgrade that's easy to install. The waveguides fit in the existing tweeter horn cutouts and there are only a couple crossover changes needed. You just remove one capacitor and add one resistor.