I've got a Buffet SDA tenor that I'm loving with one exception. The middle D blows very sharp. I know this is a problem note on most saxes. I CAN lip it down, but seems to take much more effort than any other tenor I've ever played. If I finger low D but over-tone to middle D, intonation is good, but as soon as I add the octave key it jumps up 15-20 cents. Any tips?