Disabeling Spootliht on the backup drive doesn't work

[ma012]

In the FAQ article "How do I disable spotlight for my backup drive?", you write :

« As of v2.0, when used with Tiger 10.4.3 or later, it's quite easy: just add the volume to the Privacy tab of the Spotlight preference pane. We'll automatically ensure that that state is maintained, and all should work fine. »

I'm using SuperDuper! v2.5 under MacOS 10.5.5.

When I make a full backup of my internal drive on an external drive called "Backup 1", the external drive is in the privacy tab of Spootlight on the internal drive. But after the backup, the drive "Backup*1" doesn't contain in its privacy tab the name "Backup 1" so Spootlight is enabled and I have to add the drive manually to the list.

What can I do to add it automatically ?