I build a modified version of the bill waite- penny stove It incorporates a thermal insulating cap on the bottom which uses air( an effective insulator) to prevent the problems you've mentioned. Mine also uses a cover to seal the stove completely, saving any un-used fuel. I use a combination of heineken cans and soda cans. I dont mean to brag but it's the best penny stove I've seen yet and I make them for my friends on request. My simmer ring provides a sterno flame that lasts for 45 min a a full tank.
