From the bottom:

1. TLUD Fuel chamber
2. 6" -> 4" reducer
   —off-the-shelf
   —Fits perfectly into top of paint can
3. Combustion chamber windshield & insulator
   —keep heat in the system
   —3-lb Costco coffee can
4. Tall juice can insulating the stack
   —keeps more heat in the system
   —increases gas temperature at exit point
5. Reducer used to collect and direct heat
   coming off sides of the system.
   —might be extended a bit,
   but not enough to reduce secondary air flow.