Have you compared the changed eeprom with the orginal one ? It seems that changing the region code doesn't change the data hash at all. Wondering why it is so.
Another question is, can you post or mail me the middle message hash for the new eeprom key ? Even though I still don't quite understand the internals, I believe just plug that in should work.
EDIT: BTW, When I am reading the old hdtool code and the new working one, I noticed that the working one has one more set of hash for version 9(?), why is it so ? Has this anything to do with why the old one doesn't work with some specific eeprom ?