I don’t understand why the pressure drop after the throttle plate should be such a low factor, compared to evaporation and pressure drop in the venturi.
At 50% power/50% ambient pressure, dry air would cool by around 45 degrees, and saturated air by around 20-25, i calculate that just from applying the adiabatic laps rates – 50% pressure is approximately equivalent to going up to FL 180.
My carb never shows icing, not even in IMC.
I’ve been flying around in light aircraft since the 70s, and have experienced carb icing twice, once in about 1979 flying with my dad, and once a year or so ago taxiing out to the runway. I have also been a pilot in IMC exactly once… and appreciate the attractive simplicity of the fixed jet, one moving part carburetor. 
Obviously it’s a good idea to choose the right tool for the job, and the simple aircraft is a good tool for my job.
It’d be interesting to look at the problem of induction air cooling ‘properly’ and figure it out.
With a Continental O-200 in a Jodel DR1050, using mogas, in north Scotland, I have carb ice very often. Frequently it will stop the engine immediately after start. (Checked by engineer many years ago.) With a wet runway, I have carb heat on when I open the throttle for take-off, closing it as I gain speed. A Canadian CAA document says carb icing can occur at much higher temperatures on mogas. I’ve encountered it at temperatures which seem unlikely from the diagram, on a Konsin treated runway. Carb icing is just something I have to live with, and when a student, a carb heat check every 10 minutes was hammered in.
That’s sure interesting about the mogas… What’s ‘needed’ is a complete coupled thermal/CFD (computational fluid dynamic or color for dollars) analysis, performed over a range of conditions. Yours for $500K or so, I know just the guys to do it. 
I believe there’s a fair amount of water in the air in northern Scotland
Presumably, at some point, all this will have been researched quite thoroughly so if nobody ‘knows’ the ‘answer’ it must be locked away in some corporate filing cabinet, or we’re not looking in the right place. Or perhaps it was all sorted pre-war and we’ve carried on using designs that simply work, without worrying too much about the minutiae.
