I have a The Martin Tenor that I bought recently, and fell in love with the sound as soon as I played it. Surprisingly, the ergos feel really good and accessible, except for the left pinky cluster I'm still gettin used to. The only thing I don't like are the low Eb and C keyguards, which are basically just brass rings around the keys that don't really guard. When you play the play the C or Eb, the key rises above the guard, causing the key to be pused closed when the horn's resting against me. Is it possible to get these replaced with stock yamaha keyguards or anything else? If so, who's the guy to take it to?