I just supercharged my Trangia burner tonight. I cut out the small cup-shaped bottom of a soda can, put a penny on top for a little weight (inspired by the penny alcohol stove) and put it on top of the burner once the jets were going. This had the effect of converting the stove from an open-jet style to a pressurized alcohol stove. My preliminary (and very un-scientific) test was to boil a quart of water which took approximately 7 minutes (vs. the 9 or so it takes normally).
I have no idea what this does for efficiency (or safety for that matter), but it seems to be putting out more heat.
Has anyone tried something like this before?