I'd suggest doing something completely outside of a normal props night. You'll get into the same problem that you'll be focused on the progression if you do it before or after the raid. Additionally, after the raid is a pretty late night.
I'd recommend something like a Friday at 7pm or 8pm ET, similar to our once-a-month guild meeting. This should be its own day with an agenda planned for discussion, not a late-night after-raid meeting, which isn't as welcoming to all members.
While it's always been a goal of mine to avoid overlapping content as much as possible, it's not always going to be that simple.
Frankly I don't think there is that much of an overlap between Vet-mode raiders on the Imp and Pub side. There are a handful of players that have participated in both, but each side has its own core group of consistent weekly raiders.
Additionally and more to the point of this discussion, there is very little overlap between Pub and Imp progression teams. I classify "progression" as an entirely separate pool of players from "vet-mode" and "story-mode".
until