OK, it works. For general reference, here's the sequence of events
- Download the 2 files to /Dowmload (don't try this from Google Drive, it won't work)
- Airplane Mode ON
- Open Codi Assistant
- press Advanced
- Select Flash Image manually
- Navigate to /Download and select the Firmware file, not the Resource file
- At this stage you get thrown back to the desktop with the message that Codi Assistant keeps crashing. Ignore it. it is actually still running.
- Re-open Codi Assistant
- Press Flash Now
- Spend the next twenty minutes in silent prayer.
- Airplane Mode OFF
My working theory is that Codi Assistant was stuck on an incomplete download. By pointing it to a valid set of files I managed to clear that problem.
It's worth it. My Cosmo is running MUCH cooler and it looks like the battery will last better.