Sit in a S300 and during start up, at idle rpm, look over your shoulder at the tail boom and gently move the pedals a little and see the effect that the tail rotor thrust has. The tail boom bends.
The construction of tail booms is such that they are required to bend/flex slightly to absorb the forces of the anti-torque effect and vibrations associated with main and tail rotor systems.
Agusta have had to beef up their 109 tails. EC135's early models had problems due to flying heavy police equipped machines and had to be modified to stop the cracking that was occurring.