Say the blue channel was missing from the separation prints, would it be possible to pull the blue channel from the next best negative and use it in place after a lot of fit and finish or is it completely incompatible? In my eternal struggle to create a surround mix of Pink Floyd's 'The Wall', I've certainly used parts of a deconstructed stereo mix with discrete left, right and centre channels where the movie surround soundtrack couldn't offer me the elements I needed at a given point in a song.