Im with ^^.
I've heard in multiple places that its the diff brain Servos which can't handle the 6v+ the ESC can put out.
Frankly, I'm a bit irked that the brainless Neros can't do 7.4v on the
BEC, because what that's telling me is that the servo is going to be even MORE underpowered because the rating they advertise is AT 7.4v.
Which frankly is false advertising.
The stock servo is putting out less than 175oz now because it's crippled to only 6v on ALL Nero models.