Actually, there were no ROM changes, but to make the LiIon batt work on the 5300, you should only use the original System 7.5.2 with PB 5300 enabler. After 7.5.2, apple removed support from the OS for the LiIon batt. Maybe someone who has that particular revision could figure out what they changed to make it incompatible, extract it, and turn it into a patch to be used on later versions of the SSW. A long shot, I know, but possible.