"Looking some more at Roger's articles, he talked about 9 g to boil 1 liter for Jetboil, 11.5 g for conventional upright, close to what you're saying. I assume his stove will be closer to 11.5 g since he has no heat exchanger. I bet some measurements will be posted at some point..."
Yeah, well, heat exchangers are not a magic bullet. While I made several of the things, and still use one, their action is not well understood by most. Basically, they only extend the surface area (the heating surface) of a pot. Example, the ones I made were about 17% larger in surface area for a 5.25" grease pot pan. I get about 21.65 sqin of heatable pot bottom out of a standard grease pot. After adding the heat exchanger ridges, I get about 25.33 sqin.
But I only get about 15% faster heating given the same flame on both pots. Reducing the flame shows only a 10% decrease in heating times. Reducing the flame again shows only a 7% decrease in heating times. On very low it only shows about 5% (near the limit of my tests) decrease. With a tiny flame, I was getting 20-25 minute boils but didn't show any real difference (+-15 secs) over 5 runs. It starts to depend more on heat losses than heat absorbed.
Soo, what is happening here, is that the more efficient you set the flame height (very low is the best for fuel efficiency) the less well they work. Or you can think of the simplified corallory as they only work with excess heat. (Not quite true, but close enough for camping.)
JetBoils are not as efficient as alcohol stoves. Why? With a well placed heat screen, the sides of the pot as well as the bottom are used to heat water. A typical alcohol stove set-up always includes a good heat screen at least 50% up the sides. This is largly offset by the good heat exchanger JetBoil uses. It is about doubling the bottom heating surface area. But, putting these two things together, means the heat exchanger efficiency falls off as fuel efficiency goes up. Sort of a cache 22. You don't save enough by going to low heat to make it worth it since the heat exchanger efficiency drops off quickly, too...looks to be a curve.
Basically, I am planning on using the cannister stove as a heat source in a typical alcohol stove set-up. I am hoping to reduce the ammount of fuel required to boil 40F(4.5C) water to boiling (210F or ~99C) with about 5-6g of fuel under ideal conditions in a lab. This will mean a 20% increase in the field, or about 6-7g/L.
But, anything less than 9g/L would be acceptable, given the weight for two weeks at my usage. It MUST do better than my SVEA, or I will just drop it.