Edit Suikoden III Saves

Has anyone tried editing saves for the game Suikoden III?

I figured out most of the character stat block. However when I try to
edit it and reload it, the game complains about the save being corrupt.
Editing Hugo's xp by 1 causes this error.

Does anyone know if there is some sort of hash checking going on? If
so how it is computed?

I edited the gamedata file.

I used LaunchElf's file manager to copy the save directory onto a flash
drive, stuck the drive in my computer, edited it, put the drive back in
the PS2, copied the save back to the memory card.

Before I edited gamedata, I made a backup of it. I copied this backup
onto the flash drive over the edited gamedata, copied the save
directory back to the memory card. This worked, which leads me to
believe there is some hash checking going one.

A several bytes differ in saves that are only a minute apart with no
action taken between them. Towards the begining of gamedata, I think
is the time played. But at several other points in the file a byte is
different.

Also, there is a header file that has the same name as the save
directory. This file contains the name of the Flame champion and a few
bytes that differ between saves a minute apart.

It looks like the hash or error correcting takes place on the gamedata
file. Copying the gamedata from a save a few minutes and battles after
my first original, to the over the gamedata for the original save
worked. So the other files may not be involved.

If anyone has any information, please let me know.

Thanks