David,
Every time I teach this quartet to my students, there are notes that jump out at me that make me say "that CAN'T be right!"
there's at least one Ab in the 4th movement of the 1st euph part that sounds better as a natural (sorry, don't have the score in front of me, but I will soon) and a few notes in the 2nd tuba part of the 4th movement.
I'm wondering if you've even listed your official "score corrections" for mistake that made it to print?
that being said, it's my favorite tuba quartet. I never get tired of introducing it to kids year after year.