With longer runtimes I couldn't get my 540c 9L not to overheat. Any over about 10 minutes it would overheat that was without fans. I tried gearing, but ultimately it still overheated. I finally gave up on it and got a Neu 1512. That was a huge difference. Ran so much cooler. I think you would have better luck with a 10L. Mike does have the 10L in stock http://www.rc-monster.com/brushlessmotors.php?pg=2 it is the 11th one down.