blackhand,
The tail boom on the 117 is the same part as the Bo105 tail boom, which makes it a tad short for a machine with such a substantial increase in weight and power! The increased size of the vertical stabs are to assist in overcoming this, plus the sizeable offset of the stabs helps further.
IIRC, the main rotor head titanium casting is also the same part as the 105: it must have been well engineered for the Bo105 in the first place
