Since you have a dual layer burner, you don't have to worry about shrinking as long as you burn to a dual layer disk. You can use dvdbackup. Once installed, type:
dvdbackup -M -i /dev/dvd -o /my/dvd/backup/dir/
to backup the entire DVD. For most DVD's, this will result in larger than 4.3 GB worth of files. If it is less than that, you can use K3B to burn onto a single layer disc, if it is more, you can burn a double layer disc. Type "man dvdbackup" for more information.