The ventral fin on the Super Puma was added in part to counteract the problem found at aft cg. If you rolled in to a turn and the ball was not centered (i.e. it was to the outside of the turn) in the original Puma, adding pedal would roll the helicopter quite quickly. Lateral cyclic would not stop the roll...
Aerospatiale called this 'le virage Anglais' - (the English turn) as it first happened to a Royal Air Force Puma which was fitted with the very large particle separators well in front of the CG.