Everyone tosses around the 35K rpm rule as if it's one of the Ten Commandments of brushless. "Thou shalt not exceed 35,000 rpm, or thine motor shall surely suffer!"
Maybe it's true, maybe not. I know it applies to a low quality motor like a Feigao, but what about a high quality Neu? I've never seen a detailed study showing motor temps at different speeds. Neu rates their motors at 60K max. I don't know if that has anthing to do with efficency, or if that is simply the limits of the bearings.
I do know that the mildest MM motor, the 4600, spins at 34,000 rpm with only a 2S lipo. And we all know that most people run MM motors at much higher rpm's than this. Are there different rules for a 1/10 motor vs. a 1/8 motor? I know that the bigger motor has a higher rotational inertia, but how much does that affect the efficiency of the motor at a certain rpm?
Until we see this new motor in action, none of us really knows how well it will run on 6S. I'm sure it won't be too bad, though, or Castle wouldn't risk the potential warranty costs.
With all that said, I still hope the 1700 and 1500 motors come out soon.
edit: Brian, you beat me to my point!