I just bought the LDW - 851S DVD writer a few days ago. Except the bundled DVD+R (media code: Yuden) I was able to burn at 8X, all others could be burnt at 4X only.
I have tried Verbatim (media code: mcc002), Ricoh (media code: RICOHJPNR01), and Team5(media code: 001). The Team5 one claimed it’s a 8X DVD+R, though.
I have already flashed the firmware to GS08.
The unlucky thing is that I can’t find DVD+R with media code “Yuden” here (HK).