In a nutshell: OMF's originating as 23.976 from Final Cut Pro 7 are seen in Pro Tools' Import Session Data window as 24 frame metadata. Importing a single OMF into a Pro Tools session that is set to 23.976 seems to work just fine. BUT! if the OMF comes in 2 contiguous parts and the Match Tracks feature is employed in the Import Session Data window in overlay mode, the second part of the timeline (the new material) does not have the .1% pulldown applied so the second import runs off speed at 24 frames.
Idea No. 19