i believe there is a small program that can find differences between 2 hex files
they used it find the differences between the radeon firmwares, which made us able to mod them to 9700 pro etc.
will try to find it, and try it on 2 firmwares of the plex.
i believe it is even possible to have the software adjust the differences between the hex files.
(lots of blieven in this story...because it was last year when i read it)