This is the best fan I have seen: novak 25mm fan. I just plug it into the rec and bolt it to the mm heatsink with m3 machine screws. I also space it off the heatsink 1/4" or so, that seems to help flow and cooling. Or send it to Artur and have him do the stage 1 mod. That cured my heat issue and ran fine with a 7xl on 4s in a heavy 1/8 buggy. With the new software and his mods I have a feeling the MM may work with outrunner and high loads better!
I like using the 12v models right off of the lipo (4s), you can attach the fan leads right at the circuit board on the MM and keeps the tiny wires out of harms way.