4s Rustler, which motor should I get?

The one problem I've seen with the MM motors is they seem to get hot. I have been running a MM 5700 on 3s and it gets pretty hot. Even on 2s2p 6400mah just seems to overheat when going for the long haul. I've tried to use fans but they all seem to break because of the location. price is pretty good on the MM's though. I was hoping there was something better for 4s.