Experiment to find the length away from the flaming head butt to a pot that thermal performance, the best by using perforated material at the same size is 3.5 mm.
Experiment to find the distance from the burner to the bottom of the pot to make the best possible thermal efficiency through the use of a porous material similar to the 3.5 mm.
Experiment to find the distance away from the burner to the bottom of the pot that can best thermal efficiency by using the same size porous material is 3.5 mm.