Also–the key I think is Believing the Truth, that you Don’t have to tighten your throat or clamp /engage your lips to ascend; in fact, that makes it harder.
Lead with the air, not by over blowing but just startimg with the air and engaging the corners (not the lips in the Mouthpiece, whic need to be relaxed so they can vibrate freely (faster, higher, more resonant). We don’t tighten our vocal chords to sing higher, that would hurt and sound bad…).
Use the Corners and air as your support and visualise releasing the air column through the center of the mouthpiece through the leadpipe…think of ascending as the notes being farther forward, not higher or harder..
Less air is required the higher we ascend and the notes are closer together the higher we ascend.