Hi Geoff,
ha, you've had some more and larger gigs than I have, I must say ;) I can't really comment on having a good engineer as we mix all our own stuff on the computer and just give the venue a left and right channel to use. And I think our mixes are mediocre, to be honest...
That said, I always leave the Dynamic Filter on NORMAL. I don't hear it working at all when I sing, but when handling the mic between songs the noise is just a tad better - even though the Beta 58a itself does an extremely good job of rejecting that as it is.
I never set the dynamic filter to TALK because I think somewhere in the manual it says that's for talking applications (no surprise there).
There you go, not much help, but that's what I think :D
Martin