I'd run the fan just to be safe. I've run mine in my XX4 as well but I used a heat gun and a spoon to re-shape the shell a tiny bit just to give it more headroom.
The fan cuts in only when the unit exceeds 80deg C and I did temp gun mine after an indoor club TC meet where it only got to 48 deg C running a 6.5T Losi motor on 2S LiPo. The motor also ran just under 50 deg C
