Serum, I am trying really hard.

If running through sand and stuff that offers a lot of resistance, I'd go with a 10XL and a MM (to keep costs down).

With all of the problems that I've had lately with my Quark, Compro, and Neu motor, I do have to say that my Feigao/MM setups have been bullet proof. If it wasn't for the heat issues with the Feigaos, I wouldn't be looking for anything else. I just need to be able to get through a 30 minute main.

Considering that the motor isn't getting hot on you, but the esc is, add the fan and gear a bit smaller and see what the results are.

I've been running a 12v fan that I got on ebay from a place called robobugs and have been running that fan on 4S lipo without a 12v regulator for a couple of months now and haven't had any troubles. The fan is 1"X1" and is a perfect fit for the MM. Just use 3mm self threading screws and drive them right in between the fins of the MM.