Tuba (abbreviated?)

Taylor Brizendine, blogging for NewMusicBox on the 2010 Minnesota Orchestra Composer Institute, reports on a score-editing session with master engraver and copyist Bill Holab. "Never abbreviate the word 'tuba,' " Holab advises:

http://www.newmusicbox.org/chatter/chatter.nmbx?id=6636

Which begs the question: How would you abbreviate "tuba?"