I understand that people like to make things and make pretty things. But from a performance perspective how can a box equal an open baffle? Don't think it can. The original posters speaker (Tang Band on open baffle running wide open and then augmented on the bottom using a separate amp) would sound way, way better. If you put a speaker in a box, it will sound boxy. Now you could go on and on about a single speaker and no phase shifting in the bass to a separate woofer.....but if you listened to both (done right, that is) then I cannot imagine your box speaker sounding as transparent or dynamic or deep. If you are running the Tang Band on its own amp and the woofer on another you can also put a smaller value better sounding coupling cap in your tube amp (or whatever) to ensure the Tang Band has a nice roll off on the bottom so it will play even more dynamically.
This is the open baffle forum, after all. Open baffle rules! I am sure the single driver people would love your speaker. Please post there.