The pilot receiving instruction was conducting a practice right 180 degree autorotation. During the approach, the airspeed decreased to approximately 40 knots which shortened the approach angle. At 8 to 10 feet above the ground, the flight instructor advised the pilot to apply forward cyclic while maintaining the collective position. The flight instructor then "used what was left of the rotor RPM to cushion the landing." During the touchdown, the helicopter landed hard, which resulted in structural damage to the tailboom. The pilot reported no preimpact mechanical malfunctions or failures with the helicopter that would have precluded normal operation.