Gradebook

We have some problems when we try to export grade categories from one course to another.

This is the used procedure:

1. Made a backup of the original course including grade histories
2. Restore that course using "Existing course, adding data to it".
3. Select the destination course

This procedure works fine if the destination course's gradebook is empty but we have not been able to perform that operation over a course with actual grades.

Is it possible to export/restore grade categories to a course that has already other grade categories?