Just an update. I finally got my package built.
I use ukki's script, but in preinstall.
I create the symlink.
I tried doing just that, but apparently, as it copies the data to the MMC, it tried to change the rights (or group???). That wasn't working.
So I tar'd the data and extracted it in the postinstall to the mmc.
That seems to have worked fine. I probably had my group wrong, but I was doing this on the tablet, and I didn't have enough free space to copy it to the root filesystem to fix. (My mmc is standard FAT32)

Anyway, it worked.
Thanx to arnims, ukki, pypackager, and this website.

Of course, at this point, it's only worked for me, but one user with a 770 w/ OS2006 is a great test bed. :-)

desiv