PINCHUNO wrote:
I'm no high note specialist, but I do know that "A" is much harder to slot than high "G".  IMO, "G", is the last "real" note in the trumpet range.  Even when you're tired, you can at least try to belt one out, because there always seems to be something to lean on.  G# also.  But unless you've got the breathing down for upper register playing, then high "A" onwards is a @%@@!!

This describes my experience as well.  I have a clear break at A.  When my chops are cooperating I have usable A and Bb...but I've NEVER hit a legitimate double C.  I'll confess I don't spend a lot of time working for the dubba and I'm not willing to change everything else just to get it.  BUT, if any of the pros (or anybody else) on this board who's been through this and has come out on the other side, I would love to learn from your experience.  I'm all ears.