I was able to get the product page started for the new MBM-12 Midbass Module:
But I need some help figuring out what size most people will use. I can likely get two flat pack designs made up for these.
They need to be roughly 2.25cuft before subtracting ports, braces, etc. But they can be 2cuft without giving up too much.
It turns out that the Fusion-12 Tempest flat pack can work out just about perfectly at 26" tall and 14.5" wide. I would just need to design a brace change to allow for circular or slot ports.
Tux mentioned a 24" tall enclosure, so if you guys think that's the way we should go, I can do that instead, but 26" might be a bit better and not as deep.
Another option might be something like the current 2cuft subwoofer box. It's actually about 2.25cuft so it can be modified for a slot port module with some modifications. That's 19" tall, 16" wide, and 17" deep. So it could also be laid on it's side and only be 16" tall.
I can understand the need for the shorter boxier shape, and then a taller one to sit your mains on if needed. I'm just not sure exactly how tall the other one should be.
Oh, and I would consider making up dual models as well. They will work in ported enclosures all the way down to 1.25cuft, so duals wouldn't be too big. But 4 of these in a room would be way overkill.