I don't want to completely derail this thread, but I'll make this counterpoint: There is far more convection capacity going over the R/R than there is conduction through the fender. Yes, the thermal conductivity of steel can very greatly due to composition and type, but sitting in the sun is an entirely different ball game. That is absorbing light energy which is not reflecting it, and storing it as heat.
I mean, they make heat shields out of steel, right? I figure there's got to be a reason the R/R has all those fins.
So if we replace all of the lights with LED's, we can just install driving lights, hand warmers, a cell phone charger, accent lights... I dont see any down side!
If you tear the bike down to a bare minimum electrical, how hot DOES the R/R get? What does it take to fry it? Can we add some kind of secondary cooling like submerging it in liquid or running a fan over it? Maybe the power required to run the fan will be enough to get it in a safe range. lol