if it is for frifting, which relation are you used?? I would say you should be far over 8.... around 9 - 9.5... and yes, you can mount a fan on it, no problem.
The Blue Armada: Tamiya TRF415MSXX, Tamiya TA05MS, Tamiya/Xenon TA05
Novak Brushless, Orion/Peak LiPo batteries, 5-cell
Sanwa M11 DSSS, KO Propo Servos