Blender pilot -
Just out of curiousity, what condition were the rotor blades? Old, new, pitted, etc? The engine might well be above spec, but if the blades aren't working well you won't get the performance out of the machine.
Also, was the torquemeter recently calibrated? Again, it might be denying you power.
But a friend of mine also added that somewhere around 20K, the rotor just stops working very well - he saw it in some Army testing in the OH-58 in the 70's.