Castle 2200 on 4s or 6s

So me and a couple others are having a little debate over which would be better with the Castle motor.I would love to hear what someone from Castle,and others has to say about it.IMO 6s puts the motor to high in the RPM range for everyday bashing.For occasional speed runs it should do good on 6s, but 50000 rpms seem to high for every day bashing.Since I have no Neu,are they happy in the 50000 rpm range?Actually it would seem to me like 5s would probably do good,maybe the sweet spot?But still a little high?