I was trying to think of something to do with the cheap drivers available these days (the Foster or the Onkyo from Madisound). I didn't even think about open baffle (about the only way to use the fosters).It looks like you set them up with a bit of a taper 4,3,T,3,4. Which waveguide did you use? I see it in the picture, but I'm not sure which model it is.
Why did you choose to use so many of the foster drivers - was it just so you could get the taper? I had thought about using 9 or possibly 12.