The way you guys run your cooling fans seems surprisingly effective (I double sided tapped a Yeah Racing blowing back onto the motor), I don't usually bother on my 10.5 racing at night here, but I set up a fan on the chassis powered off the battery cause I'll be running 17.5 during the day soon.
Testing it on Friday night, I was very impressed by just how cool the motor stayed, I set some good lap times with the 10.5 running under 50C or so, timing up around 35 on the Thunder Power, so I figured I'd go up a tooth.
But on the track layout we were running, I went slower, even when I upped the timing to 40 I did not match my lap time with a tooth smaller.
It's possible (I'm guessing a little here, still not that experienced with electric) I may have geared past what my Turnigy Nano Tech 5600 was able to keep up with punch wise, cause I felt like I lost a bit of punch.