Here's a thought...... Talking to a respected trumpet teacher, he mentioned how he normally starts trumpet students on 7C (because that's what the instrument probably came with), and later moves them to something like a 3C. Much farther down the road, to something like a 1.25C or something aound the "1's". He increases the mouthpieces size over a very long period of time, deepening and widening as the student is able. However, in the brass band world the "one mouthpiece for life" attitude seems to prevail. (Bit of a generalisation, but you know what I mean!). I have to wonder is there merit to starting someone on a relatively shallow mouthpiece, let them gain a resonable range and a bit of experience, then graduate to a more "classic" cornet mouthpiece? Tone might be sarcificed a little initially, but we're taking a long term view here?