My ethernet upgrader tool has now been updated to include a --extract option to unpack a .upgrade file into it's (gunzip'd) components in the current working directory.

Usage: ./upgrader --extract car2-developer.whatever.upgrade

Afterwards, one can then (on Linux) access the actual would-be empeg filesystem using this:

mkdir t
mount _dev_hda5 t -oloop
cd t
ls

upgrader-0.8.tgz is attached.

Cheers