doubleofive said:

Did you just put the matte on top of the image, because if I recall a lot of the scenes were reframed for the 2.35:1 version. You may want to reframe some shots, especially look at the video log scenes as they were rendered to fit in frame on the 2.35 version.

I'm not sure where exactly you heard that, but from all of my composition tests and video comparisons from the film's scenes and the "scope version" deleted scenes (the ones which used the exact same shots as the 16x9 version), it seems like the filmmakers really did just add a black scope matte over the video for the 2.35:1 version of the movie (Cameron did frame the entire film for both 16x9 and scope ARs while in post, so that makes the most sense to me based on what I've seen and tested).

(also the video log scenes, which you mentioned as being rendered to fit 2.35, in fact don't completely fit the scope frame and cuts off slivers of the top/bottom text graphics - even if you reframed the shot, you'd lose either the top graphics or the majority of the bottom graphics)