Very cool indeed. I also did not want to purchase a Weber lid, but I can get a tight-end drum for $10 that can be cut at whatever height I need.
In my original post I included a URL to this guy who created a short smoker for more efficiency. (http://www.shortypen.com/projects/bb.../uds/index.htm
One thing I forgot to mention, is that I put a thermometer on the lid and one on the side of the barrel at grill height. These thermometers are showing like 75 degrees lower than my remove thermometer located in center of cooking grate! I know the thermometers work because I used them on my previous offset smoker and after laying down tiles to make the heat from firebox move all the way into the cooking chamber, the temps all around were within 10 degrees.
So is it normal to have 50+ temperature difference on the side and lid from center of cooking grate? I do not have any diffuser but certainly will put one in to test.