I don't believe the word "should" is used in certification of airplanes.


It's not in 14 CFR 25.109 Accelerate-Stop Distance (Airworthiness Standards: Transport Category Airplanes)

It's not in 14 CFR 23.55 Accelerate-Stop Distance (Airworthiness Standards: Normal, Utility, Acrobatic, and Commuter Category Airplanes)