Ah, a paint can.

Now, that might work. And it doesn't have to be as efficient as a Caldera Cone to still be a good stove.

Definitely an important thing to find a pot with a rim. The pot rim needs to mesh with the rim on the paint can to support the pot at the correct height. Either that or you'll need to rig something up inside the paint can.

I've found that a pot height of about 2 to 3 cm above the burner seems to be about right.

The other trick is to get the ventilation right. Too many openings, and your system doesn't work well in wind. My experience is that wind resistance is still important even when car camping. Too few openings, and your stove will be starved for oxygen, and you'll get a lot of sooting. You also need the placement to be correct so that you create the kind of controlled air flow that will optimize your heat transfer. Generally, you want more holes at the top than at the bottom.

I guess better soot than a stove that gets blown out in wind (in other words better to have slightly too few than too many holes), but better still would be a system that really works well.

HJ