Av8tor, you raise a very valid point about the lead in AvGas. The 100LLAvGas was actually a compromise between the aviation industry FAA and EPA. All of the older engines required some lead in the fuel to prevent valve failure. I don't remember all of the details, but the Continental engines would experience valve failure with as little as 200 hours operation on no lead gas. The Lycomings were not as bad, but still experienced premature valve failures. It all had to do with the metallurgy of the valves and seats. Consequently the lo lead 100 octane was approved. Plug fouling due to the lead was never the problem. The Lycoming IO 540 in my Cherokee never needed plugs before the 2000 hour engine overhauls. The lead would be a poison to the platinum on the glow element over time.

I have an OS 60FP that I modified the carb to be able to run on gasoline with spark ignition. Using a 13 X 6 MA (black) it would turn 11,700 on glow and 11,300 on gas with spark at 30 deg BTDC. Over the weekend I'll pull it out of the box and try some runs with different fuel mixes.
This won't be completely applicable because I'll have to use 18% oil. It might point in a particular direction.

Intuitively though, I believe that the best performance would be a mix of gasoline, methanol or ethanol and acetone. Probably around 15% methanol or ethanol and 5% acetone. I'm not sure about the Coleman fuel, since it is blended at a much lower vapor pressure because of safety concerns. However in a blend with the alcohol and acetone it might not make any difference. Hard to say.

As far as costs are concerned, gasoline is about $1.40 a gal. Methanol can be obtained for about $2.50 a gallon. Denatured ethanol is about $5.00 a gallon and Acetone about $7.50 a gallon. This would equate to about $2.00/gal using methanol and about $2.30/gal using ethanol.

I'll try a few runs with the 60 and post the results.