How important is the lip?
It’s only function is to vibrate. To prove the point you can even produce a sound with your tongue stuck out in place of using the lower lip because it too will vibrate. You could potentially develop an embouchure any place on your lip like Gordon, Mendez and Herseth. Claude used to demonstrate a three octave chromatic from low G to G above high C while at the same time sliding the trumpet from one corner of his mouth to the other corner. The top lip does vibrate better and will get the best results.
