Actually, all my original designs were three-ways, as shown in the PiAlign.doc. The drawings and formulas are really more of a description, or an outline, but the original speakers were all three-ways, nonetheless. Only the one π and two π were two-ways.After about 1990, I started making some large two-way systems and I really liked them. With the right components, you lose little but the cost. But I've taken the cornerhorns back to a three-way because I think it makes more sense for that design. The one π, two π, three π and four π are all two-way speakers.
As for the ten π, I'm still asked for those a lot. Most people use the bass bin all by itself, and it works great. My favorite was always the seven π, but when I moved into the home I live in now, it didn't have suitable corners in the living room, so I had ten π's built instead. They are hopelessly oversized for the room. Sound great, but they are very imposing.
Have you seen the new little eight π's? I think those are a lot of fun too, so check 'em out!