HI. Interesting point this. I have been playing on larger mouthpieces but have been recommended a smaller piece by a friend and it does help. I am now working about 3C size. However, I have never been able to play on shallow mouthpieces. I tried a Marcinkiewicz Shew 2 some years ago and found my endurance disappeared and on one quintet gig I had to play the last 10 minutes on a Flügel as the chops had gone. Since doing MTM for over two years, and still realising how I am still way off getting pure process, I am starting to experiment with the Shew and find I can play it across the register with a break around A above the stave. If I then back off and focus on the aperture the lower lip seem to roll out and it becomes easy to play above the stave for a short time. I even played 3 octaves chromatic C-C last week. The more I focus on the early stages of the course the more this seems to work.As my playing is focused on the middle register in a jazz combo I do not really need that register but it is nice to have the option.
Paul