So I ended up with 22GB in the backup file.
It's nice that the evernote-backup program syncs, so that if it fails at any stage (due to internet problem or whatever) you just re-run 'evernote-backup sync' and it goes from where it was.
When I look at the data in the SQL Lite file the title for each note is readable, but the note content is just code so don't expect to look at text or images etc. in the notes.
Anyway it served it's purpose for me and was quite fast. I will need to test recovery to be completely happy.