These are the steps that I use.
9 gig disk to 4.7 gig disk (dual layer to single layer)
1. Decrypt disk using DVD Decrypter in File mode
2. Use DVD Shrink and open the folder where the decrypted files are located.
3. Either reauthor or full disk back up (you can use DVD Shrink to remove regional locks and other useless menus, extras, voice over, and subtitles).
4. Put in blank DVD, and press Back up
Disk to Disk copy (1:1 copy)
1. Use DVD Decrypter in ISO read mode.
2. Put in blank media when finish copying.
3. Use DVD Decrypter in ISO write mode, point to where the ISO image is and burn.
With DVD Decrypter you shouldn't even need to use NERO.