I have read several times that a good trumpeter can get the job done with any reasonable mouthpiece. So I have just proven what a hack I am. I misplaced my faithful Curry 3C dot (Don't ask). To get on with some practice I grabbed a Bach 3C I have and started with my regular routine of soft longtones from Schlossberg 7. By the time I finished 3 of the 4 lines I felt unusual fatigue and was not holding the notes quite as long. Definitely feeling the sharper rim. So I stopped and later retrieved my Curry. Now things are good (relatively) again. If you find a mp that works for you, don't be in a rush to search for a different one.