RE: It really is hard.
Depends what heli you have...
I would put it like this. Little fp's (Walkera Dragonfly #4): balancing on a broom stick, Little cp's (E-Flite Blade CP): balancing on a baseball bat, medium cp's (Align T-Rex 450, Kyosho Caliber 3): balancing on a cricket bat, big cp's (Align T-Rex 600, Kyosho Caliber 5/90): balancing on a tennis raquet.