I have been using a Bach 5C mpc with my Bach Chicago C trumpet. I love the tone, response, and intonation-hasn't been a problem. But now that I am getting proficient with my C (playing Bbs feels like playing toy trumpets/vuvuzelas), I am noticing that my upper range is quite flat. I can lip up a little but not enough. I tried a 3C mpc...my response improved and tone became richer...still no difference in upper register though. What can I do?!