ORIGINAL: downunder
The flash point of nitro is 109F and boils at 214F while methanol is 61F and 147F. I can't remember ever having a fuel problem even on days well over the 100F mark in the shade but I do remember putting a thermocouple down below the spray bar on one engine at full throttle and there was a temp drop of about 20 degrees. This would have been from a combination of the fuel (mainly the methanol) vapourising and the lower pressure.
So your of the opinion that the methonal and nitro are not evaporating ?... Also you have no problems with 4 strokes at 100 plus int the shade ?... Wonder if the fuel brand/mix has anything to do with it... I now have a cover for the fuel can to keep it out of the sun.. I will try it next Tuesday.. Figures though now we have a cool down started.. Mid 90's forcast for next week...