Thanks pitchlink,
It was really a question.
I was just thinking about the possibility that at 90% we were using more pitch, more thrust from rotor, and all the possible power from the engine,even at less rotor speed.
Now, re-reading the posts from Geof,bpaggi and you. I understand the NR droop is just a "tool" to jump into flight,
The droop is allowed up to 90% and is not meant to achieve a better efficiency but to convert the huge M/R inertia into transational lift
Regards
Aser