THE PLT INITIATED A MAXIMUM POWER TAKEOFF FROM A CONFINED PARKING LOT WITH 2 PASSENGERS ON BOARD. THE AREA WAS BOARDERED BY OBSTRUCTIONS & PEOPLE. THE PLT RPRTD THAT DURING LIFT-OFF, SHE INCREASED POWER TO 2900 RPM, LIFTED OFF TO A 4' HOVER WITH 33' OF MANIFOLD PRESSURE, THEN BEGAN A MAX PERFORMANCE TAKEOFF, 'PULLING POWER AND TURNING THROTTLE' FOR EXTRA RPM WITH SLOW FORWARD SPEED, REACHING 36' OF MANIFOLD PRESSURE. AT APRX 15' AGL, THE PLT NOTED A DECREASE IN RPM. SHE INCREASED THROTTLE APPLICATION, THEN DECREASED THE COLLECTIVE, BUT WAS UNABLE TO RECOVER THE LOSS OF RPM. SHE MADE A LEFT PEDAL TURN TO AVOID OBSTRUCTIONS & PEOPLE. SUBSEQUENTLY, THE HELICOPTER TOUCHED DOWN HARD & WAS DAMAGED. AN EXAM OF THE ENG DID NOT REVEAL ANY DEFECTS. THE FLT MANUAL WARNED THAT LOSS OF ROTOR & ENG RPM WOULD FOLLOW WHEN THE ENG WAS OVERBOOSTED. AT 36.5' OF MANIFOLD PRESSURE, THE POP-OFF VALVE WOULD HAVE ACTIVATED WHICH WOULD HAVE RESULTED IN A SLIGHT POWER LOSS.