Off the top of my head I'd have to say that warmer fuel would actually produce more power because one of the things that methanol does when it passes through the carb is to begin to evaporate. Methanol has the fortunate ability to take a lot of heat out of the air as it evaporates (it's latent heat of evaporation is extremely high compared to other fuels). This cooled air takes up less volume allowing even more air to get into the crankcase so you end up with a greater mass of air. On top of all this, our engines rely quite a bit of the cooling affect of the evaporating methanol to the point where, if you run the engine rich enough, there's no need for any external cooling from the propellor.

Nitro doesn't cool anywhere near as well from evaporation as methanol does but because you can feed comparatively huge amounts (by volume) of nitro in this makes up for it.

As for the crankshaft, they always run cold because of the fuel and airflow inside them so they're self cooling. With a plain bearing engine you should be able to touch the crankcase under the bearing area and it'll feel quite cool even at max revs. If it feels warm or hot then it's too tight and is generating heat from friction so it needs more running in.