Thanks.
I always though so that V1 should be lower when derrating.
But captains add a few knots when using flex cause they say that if the real temperature was 50ºC and elevation 1000ft (or what ever the airfield elevation is) the speed booklet adds some 2-5 knots to V1 and 2-3 to Vr.
I never say anything cause I am a copilot with limitted experience and in any case those few knots dont make a big difference. As derrating only takes place on long runways.
In the case of the footprint.
How do you know, when you are high enough so that that higher power setting causes less noise that if you were lower with a flex power?