My database has ~36 MB. The db-on-scard feature was developed because lower-end devices (including my own back then) had problems with these db sizes.
The problem I wanted to raise here rather is, that the user has a hard time of doing this correctly. The only sure way of doing it is (if I got the details correct):
- stop/kill c:geo in main screen
- copy folder
- start c:geo, go to settings, change the folder
- delete folder in previous location

Too many places for the technically not so inclined to break things and loose data IMO, leading to frustration and too much support mails in turn.