I made one out of a heineken can and a sardine can that works pretty well. Burns for about 15-20 minutes total.
I have built a few others too and I think they work best when they are about 2x as deep as the diam.
You definately need a lot of holes in the bottom of the outer can and a lot on the inner can too. That lets air into the side chamber up the sides and out the top into the combustion area chamber and thats what makes it burn really hot.
Pics. You can see how many holes I have in the inner can.
I came to the conclusion that the insulation was not worth the weight on this one, but it did help a tiny bit.
The wire grate did not really help either. Gots needs a lot of holes
I am going to work on another similar one this weekend.