[Zope] repozo, pack and backups

[Miles]

Hi,

I'm hoping someone can share their experience of using repozo, packing 
and backups to answer a couple of questions.

I've googled around to confirm that packing means a full backup.  Is 
there any way to carry out incremental backups and then pack the 
database, without carrying out a full backup each time - for example, 
can I continue to get nightly incremental backups if I pack nightly but 
retain the last 2 days' transaction history?

(I transfer the increments to a backup server, and then rebuild the 
database, then take a nightly snapshot to tape, so I really don't need a 
full backup)

I have an inkling this is not possible, but would be useful to confirm...

TIA,

Miles