I finally printed a mouthpiece that sounds the same as my Bach 5.

New in Version 2.1: Works with Makerbot Customizer
New in Version 2.0: OpenSCAD Parametric (make a mouthpiece for any brass instrument)

I print these with my Makerbot Replicator: in ABS at 20% infill and 0.15 mm layer thickness and sand the rim with fine sanding paper (400). Let me know if different settings work better.

Use OpenSCAD or Makerbot Customizer to get your custom mouthpiece.

I have included values for:
Trumpet (Fist hand tested)
Trombone (Let me know if these are good values)
Please let me know good values for Tuba, french horn, etc. Everything is in mm.