Fred Ireson is a big fan of the Karlson enclosure. It is interesting looking, isn't it? If I were to build one, I'd probably be inclined to tune the motor chamber the same as I would a bass-reflex cabinet that didn't have a Karlson aperature.If you need any software to help design the cabinets, there are some great programs in the "info" section of the π Speakers website. Look near the bottom of the page and you'll find them.
Keep us posted on your speaker project and post some photos if you can when you have them finished!