I wanted to share an idea. I have tried to make a few of these updraft stoves and when it is really cold it is hard to get them to light because the updraft is not hot enough. I could add a layer of insulation but instead I decided to make the updraft come from the center. I made a prototype out of a 28 oz tomato can and a 12 oz tomato soup can. I am happy with the result. I clearly got a good secondary burn and I think it is the simplest design that I have come across. I put the third can on top just to show that you could cook on the stove as is in another 12 or 14 oz can - have a look.