This is kind of along the same lines...but most of the trouble ensembles
have (that I've seen) isn't from defining subito forte, but rather from
playing it differently than a sforzando (sp?).  The main difference being:
one is a dynamic level (sf) and one, an effect (sfz).  Our conductors have
a horrible time, every semester, trying to get the students to get
immediately piano after an sfz, and staying loud after a subito forte.
Just a sideline that I thought I would add.

Kim Martin