Well, I think I’ve sorted this out, and the issue was that the V1U footage was shot in regular 24p mode, not 24a – thus it came in as 24p with pulldown added up to 29.97, and those extra frames weren’t stripped out on import. So I can either reverse telecine everything, or just edit in a 29.97 timeline.
One question for FCP framerate experts out there – when you put such 24p footage (ie, 24p in a 60i wrapper) into a 23.976 timeline, how does FCP determine how to deinterlace the footage/remove pulldown? Like I said, most of my footage was fine, but definitely not all. And I swear there were clips that would play smoothly (deinterlaced correctly) sometimes, and be jittery (deinterlace incorrect) other times!
Thanks!