Dave, I would neither consider myself to be either an upstream or downstream player as I hold a trumpet generally close to level. Too, I try to keep either lip from actually entering the mpc cup as I'm certain such would alter the internal design of the cup producing inconsistent variations in the sound produced
Too, I believe all the various kinesiology visual studies of the lower lip vibrating are only false allusions, truly being only a flutter / waver in response to the upper lip vibrations. Yes, too I can finger isolate the top lip and vibrate / flutter the lower lip, but I've no control of it as I do with the upper lip in forming an aperture with control by my facial muscles viz the whole embouchure. I know of no cinemagraphic visualization performed at film speed faster than 24 frames a second as otherwise they'd become a blur to the human eye, and yet there is presently a scientific camera with a film speed so fast that it can reveal a bullet's rotation in flight or the electronic pulse in computerized circuitry. Still, I'm sure there have been advancements in the technology of this camera in the time lapse since I once utilized one with spin-offs in such technology to other imaging equipment. When I used this camera, it was known as a Fastex camera, but what it is called today I really don't know, but one can Google Fastex Camera and quickly confirm the film speed is about 5,000 frames a second in a study by the University of Michigan on steam turbines ... and this wasn't yet digitalized imagery.
Yep, no way in my mind can one humanly discern actual movement at 5000 frames a second and no musician I know of can play that fast. Taking the pictures was the easy part. The analysis of each frame was the arduous and tedious part, even when divided among hundreds of analysts. I would have welcomed it had such a camera been on a C5A when airbourne, but alas it was not and the plane it was on made it very cramped to operate. Too, it required intervarometer integration to the aircraft speed as caused me to wish I could cuss at times (maintain radio silence). Still, I could smile when the final status was acclaimed, "Mission Accomplished", and I must say it was a team of 4 of us that operated that camera making sure that many film cannisters rotated in place precisely and that all systems were maintained with optimum accuracy. Thankfully, never saw that plane or camera again, but I have seen Fastex cameras otherwise as a civilian.