"A negative for aft cg is that the rotor must be flapped down to get the high speed thrust, so the flapping could be a maximum, as would the shaft bending. These might cause shorter shaft life and therefore they might knock down the Vne a bit."
AS-350 B3 pilots: reference Sup.2 VNE limits pre-mod 07 3024 (which removes the gurney flap from the horizontal stab).