I recently purchased the Sony DRU-710A, so I could backup my movies in full quality DL format. It only burns in DVD+R DL. So will I need to buy 9.4 GB DVD+R's in order to backup a large movie at full quality. Or will it burn dual layers on a 4.7 GB DVD+R. Not sure if they even make 9.4 GB DVD+R's? Can someone please help??