This was discussed a few weeks ago.
I would go another route if it were me.
Unless you have a cheap and endless supply of fuel for the thing.
The one that was built a while back was a fuel hog as BigT and Frank Cox mentioned in the post I attached below..
http://www.smokerbuilder.com/forums/vie ... 31#p121131
Frank has some recommendations in this post also, but it seems ,like it is still a working theory. Unless you wanna take on a challenge and go with the recommendations. It would actually be pretty cool once any bugs are worked out of it if any..
If It were me, I would think about revamping the offset that you mention (if needed) or making a reverse flow out of it.