We don't recommend 3s because if we did, everyone with a 4wd SC truck would immediately try it... And that motor isn't appropriate for 3s in a 4wd SCT truck.
Both the motor and controller are 3s capable, in the right application... But not in a 4wd SCT truck.
So yes 3s is ok... in something like a rustler... I will.
Maxx - FLM, MMM, CD Med.36x706s
Raja - FLM Ext. MM, 1512, 4s
SC8ight - MMM, 1520, 6s
D8T - MMM 1717 6s