[louabill]

Thanks for the quick answer. So... the proper procedure would then be

1. Backup laptop using "Erase ... then copy"
2. Boot off backup
3. Turn on FileVault
4. Shut down
5. Boot off laptop
6. Check that backup works without hassle

This is indeed much simpler.

I'm posting this so that there is a place I'll find it the next time I get confused. Happens all the time.

Thanks again.