I have the 1520 in my RC8T FT running on 5S with 15/52 gearing. It isn't all that fast but it's all that my local track can handle. Heat? What heat? Everything is almost ambient. I don't even run a fan on my MMM since I broke the last one. Great motor.
Also tried it with 20/52 on 6S and it was just insane (This time I used a MMM that had a fan) and it was just great. Wheelies and front tires ballooning like crazy. No real heat on the 1520 to speak of. Say about 100-110F maybe but the ESC was a little warmer than I like to see it.
All in all this has to the best $65 that I have ever spent.
Yeah... the motor seemes to like the higher load setups as the temps were quite good through the run... If I get the chance... i'll do some temp checks and post up the numbers tonight...
not sure how long the tyres will last with the punishment they are receiving though ...