Mouthpiece placement is very individual. It’s the one thing a teacher can not tell you how to do because everybody’s oral cavity is different. People that play well, have their endurance, flexibility, range, etc… is because they have found their “Sweet Spot”. Everyone has one, it’s a matter of becoming very intimate with your mouthpiece placement and finding it. WAY more intimate than your thinking right now. Your sweet spot is the placement that does not interrupt air flow and allows it to flow with no eddy currents being created in your mouth. There are other factors such as stance, upper body relaxation, compression, etc… but I’m only talking about your sweet spot because this is what I think you are talking about in your post, mouthpiece placement. When you get on it everything will start to snap in place for you, you’ll notice improvement, sound, and all the above mentioned characteristics moving forward and up. This is not easy, and takes time, patience and a smart approach to your horn. For instance my sweet spot is centering the piece on my chops and then moving the horn slightly down and left to a lazy 7 O’clock position. It DOESN’T MATTER what mouthpiece I use this is my sweet spot, and it’s a very small area, not much room for movement, but when I’m there it’s a feeling I have a hard time describing. My whole head vibrates, the horn vibrates, my sound is huge and I think of my sound way out past the bell and I describe my sound as Laser because that’s how it feels. When I’m not on my sweet spot it’s just plane old hard work : ) Play the trumpet with your BRAIN not your Brawn....Hope this helps !