It just occurred to me that those of us using aux 6 for an aux driven sub can now assign the Master L&R fader and Master Aux 6 fader to a VCA and use the VCA to control them together! Previously you had to change the two masters separately to maintain the balance a bit of a PITA.
I also seem to have found a bug where if you go to a VCA's assignment screen the aux and L&R masters aren't a choice but you can assign those on the individual control's assignment screens.