addison, it took a lot of testing and a few prototypes to get to this point.
And as Bob notes, heat/wind screen is critical part of it, especially with narrow pots. With wind, you have to stick the stove/wind screen behind something to block the wind otherwise the turbulence really messes with the cooking times and speeds.
Note that if I had a 1.3 liter or 0.9 liter evernew wide pot, I'd be getting better efficiency, but I think I did ok with snowpeak narrow pot, about 700 ml or so, not sure.
The real penny stoves, by the way, use the top of a can to form a base, which then creates a small insulating layer of air to help keep the alcohol warm. I never tried using aluminum foil on the ground, but that would probably also boost efficiency a bit.
By the way, the priming solution for penny stoves found online, creating a base with slots / spaces cut in it, to pour alcohol in, is a very bad idea since you are removing the insulating layer. I was able to easily see this problem at normal temperatures with one of my less successful prototypes, that already didn't burn hot enough.
A few other things, don't punch a half circle of small holes around the bottom for air, cut one large rectangle, 1x1.5 inches or so, that way you can point the air hole away from wind. Then you can even make an aluminum tunnel of sorts for that, though I didn't find that did much when compared to wind blowing over the top of it. This air opening needs to be under the slot you make for the pot handles, if you have handles.
Don't know if it matters, but I'm using a 3 leg bicycle spoke pot stand, which gets very hot as well, sometimes red hot, and probably helps a bit transferring even more heat to the pot.
I also got tired of making different sized heat / wind screens to test different diameters so I just drilled 3 holes top and 3 bottom and use wing nuts to pick the ideal diameter for the pot. That works fine, and also make it very solid when i put it together, and it rolls up and fits in the pot, sticking out of the top, then I just put the lid over it and put it in the snowpeak stuff bag, just fits with cozy.