Been coming in to work smelling like a hippy for the past two days because of this!
Made two prototypes, still needs a bit of tinkering, but so far I'm impressed.
The first one was with a 840ml can of beans on the outside and a can of catfood on the inside which turned out to be too narrow. Now I found a can in between those two sizes, works better, more space for wood..
Once I figured out that lighting the stove from the TOP is imperative I got much better results. Right now with a very much imperfectly sealed stove I got a good-burn time of ~15 min. It took me a bit to cop on but the idea is simply to build a fire on top of your already filled stove. I've been putting the sticks in vertically to get as many inside as possible and still have air-flow. And I *think* they burn slower this way.
It uses very little wood considering the ammount of burn time you get, meaning you can use it just about anywhere. And no smoke means it's stealthy.
One of my objections is that it's bulky unless you're carrying a pot that you can fit it in to. This is also why I refuse to make it any taller than the can I'm using now.
Another objection is that once the fire burns down, you have to add sticks, creating smoke, and the fire is burning from the bottom again, unless you start all over again. So it's good for a stealthy cup of coffee but not a proper meal, unless I manage to get it going for 45+ mins, but with this size can I can't see it happening. May post pictures soon for all you backwards hicks still using the imperial system to give you an idea of the size. ;)