Well, here's a quick sample of a feathered mask. It's 5 pixels around the edge, which covers the worst of the various distortion while preserving most of the picture information.
No idea what this will look like in motion, of course - I can imagine that the softness would be fairly distracting on smaller screens (if the image isn't filling your field of vision).
The idea of cropping off pixels altogether is troubling, though - particularly considering how much the image has already been trimmed on this print. Having said that, have you checked to see if the re-framing is uniform throughout the film?