The space issue caused by 3.7.2 really should be stickied given how widespread the issue is.
For anyone else that found this, this is how you downgrade from 3.7.2:
1. Download 3.7.1 KoboTouchExtended.zip from
https://github.com/jgoguen/calibre-kobo-driver/releases
2. In Calibre, go to Preferences -> Plugins and click "Load Plugins from File", select the zip file downloaded from the step above.
3. Restart Calibre.
4. The affected books need to be re-uploaded to your kobo devices.