MadDog: glad you were able to figure it out!
I got tired of the usual inlet/outlet scheme. I needed something that would allow for an unencumbered outlet (read: less restrictive). I'm surprised no one used it before.
The cube can be just about anything. A plexi cube with two 1/2 barbs on it should do. Think about a cup, where the twin tube is attached to the top opening, and the 2 barbs are stuck at the bottom of the cup.
I've got some preliminary drawings from Utabintarbo.
I also got in touch with Fixittt, who tells me that a 1/8 inch endmill is about as small as he can go, so I'm running new numbers.