Most everything is the same except the motor chamber layout. The new version is a little easier to build because it doesn't need the fill, and the chamber sizes are nearly ideal. But other than that, they are very similar horns.

Be aware that the 12π hornsub is very large and powerful. It is overkill for all but the largest rooms, theaters and outdoor use. I designed it to provide very high fidelity at high power levels, the kind of thing needed for outdoor concerts and the like. So it is probably a lot bigger than you need.

Pro seven π cornerhorns are tuned to be slightly overdamped, which makes a good conjugate for corner loading. Pro four π speakers are too, for that matter. They work well in small to medium sized rooms, and don't become boomy when placed near boundaries. They are designed to work best with boundary reinforcement. You'll get good response to 40Hz with a 2226 in these designs, even without a sub. And they aren't terribly large, so they don't "take over" the room.

Very large rooms have different requirements than small to medium size rooms. You won't pressurize the room and get "cabin gain" in a large room or outdoor space, so tuning is a bit different. And you expect to push the speakers much harder, so you want to optimize performance at high drive levels. For example, it is easy to generate over 100dB in a medium size room with very little distortion from a good quality direct radiating woofer. One hundred feet away from the stage at an outdoor concert is a little different. That's where the advantages of a large push-pull basshorn become apparent.