Did you try the Book Type Utility? If you tried the Omni-Patcher, it would likely give some error message since Omni-Patcher only works on LiteOn 1693 and older models. Which firmware is currently used?
The 165H6S should do bitsetting on DVD+R DL discs by default, you can use Nero CD/DVD Speed or Nero Disc Speed to check the current settings. with this tool you can also change the booktype setting.
give it a try
OK! i did it, heres what the problem was:
my drive was reading as having firmware HP16 (probably OEM from HP) so i just had to manually change the firmware to the latest. the standard Liteon update didnt work either, had to use liteon patching utils. after that it worked fine
Glad to hear that you solved the problem, and thanks for letting us know the solution.