We can also used that feature to compress extras. lets assume we have s source that looks like this:
VOB 1, main movie, 5 gigs
VOB 2, The making of extras, 2 gigs
all other vobs plus VOB 1_0 = 300mb
To make a complete backup, set size for the main movie at 3gigs. Then run DVD2one with the "making of" has source and set size at 1 gig. Then copy all other vobs in a folder plus the 2 re-encode set of vobs and you have a full DVD-9 to DVD-5 backup.
DVD2one is so fast it pretty doable depending on the structure of the source DVD.