Check out the following website for info. Off the top of my head there are only four single driver fans/users who frequent A'Gon (better off with a specialized group).
Sure it is good for the money spent and there a number of designs out there. The 206e is designed for back loaded horns. I've heard good and bad but can't comment on most because there are few out there.
Here is one recommended by Fostex in case you have not seen it.
Dekay gives best advise. Do a search at that forum, study up, identify a couple designs that look decent, and ask questions over there. There are very few diy full range folks at this site and probably nobody who has significant hands-on experience with that particular driver. (watch'em come out of the woodwork now and prove me wrong! hehe)
I'm not sure if you're still interested, but I just finished building my first speaker project: FE-206 drivers in the Fostex recommended backhorn cabinets (www.madisound.com). They are currently breaking in and sound great. They sound much more extended in the highs and lows than the pair of Hornshoppe Horns that I previously owned and they were fun to build.