That's what I did originally. You have two options:
1) Hex-edit the .exe to play movies in your resolution, in my case, 1920x1080 (and, of course, edit the .ini). Upscale the HQ movies from their native resolution (1600x680, usually) to your desired resolution using RAD Video Tools, in my case, 1920x1080, and then use the newly-converted movies in your Movies folder. This will play the movies in-game at 1920x1080, no black bars, full-screened, at a resolution and quality level higher than default, but for some reason, not as good as they look when played through RAD Video Tools.
2) Hex-edit the .exe to play movies in your resolution, in my case, 1920x1080. Don't convert the HQ movies at all, place them in your Movies folder, and let the game upscale them for you. In the case of 1920x1080, I'm assuming the resulting resolution is 1920x816, which maintains the ~2.353:1 ratio of 640x272.
What I was saying was that I was seeing if I could upscale them from 1600x680 to 1920x816 myself with RVT, and then edit the .exe to play at 1920x816, in the hopes that there would be higher quality because I did the upscaling beforehand, instead of allowing the game to do it. But I couldn't get that to work.