In reply to Bog ninja:
Do you know if it matters whether the stove legs are on the heat exchanger or pot base? There isn't really any mention of it in the Primus manuals (only "With a frying pan or large pots (Fig. 3) IMPORTANT! When using a frying pan or other pots than the PrimeTech™ Pot 1.0 L, do not use the wind screen (5)!"), otherwise there is just a symbol on my Eta pot showing not to do it.
I have heard that CO levels are raised when the flame isn't combusting fully, but wouldn't everyone with a standard flat based pot have that issue?