My thoughts on flute and music.
I have found that a "lighter touch" (from the lip plate on the chin) facilitates the production and control of the high register. I have used this in performance on both flute and piccolo with tremendously positive results. Tapers, pianissimo playing and control are greatly enhanced! This is generally accomplished by releasing the pressure and leverage from the left hand (as it contacts the flute body). A player would have to hold the flute in a modified Rockstro position as shown in the photo. At this point, the muscles of the lower lip are freed and can gently come forward (as in a pucker or kiss) to refine and concentrate the air. A lower volume of air (at a faster speed) results, which when properly directed (higher on the "strike edge", farther out of the embouchure hole) emits a well controlled, soft high note. This procedure works particularly well on the piccolo. I have found that a gentle touch (from the piccolo headjoint as it contact the lip) is generally the rule as opposed to pushing in. Piccolo playing becomes easier and the lips naturally respond to a more forward position.
I am a freelance flutist, performing and teaching in San Diego, CA.