RE: largest electric?
I know what you're saying ea01bg but I personally wouldn't use a 401 in a 600 size heli. Maybe that's just me but if I wouldn't do it unless I couldn't afford anything better. The servos are not that appealing and the battery sucks.
If you're willing to spend the money on a 600 size heli then do it right... That's my philosophy but to each their own.