Some of the sites that show how to make a stove mention the wind screen is as important as anything else. Big temperature difference with vs without. Doesn't have to be fancy, just something to keep the hot gases in contact with the pot as long as possible.

Edit:
Oh... and I discovered the burner hole size, number and placement are fussy and critical. Too many, low pressure. Too few, low pressure. Too big, low pressure.

I've made, I dunno, 10? of these so far. Two work really well.