Thanks for the good responses.
Portamento is a reason for setting to mono, although I tend not to get on with it too well (on other than on the whistle!). For slides and legato type playing on saxes/trumpets/human voices, I use custom voices which can bend in pitch or lose the attack depending on how hard or soft the notes are hit.
IMO you can get much more responsiveness than provided with many of the SA voices.

John