I did this recently and had a similar situation where my drive was id'd as an 811 but any disc in the drive was not recognized as being there.
I finally figured out how to do it.
Step 1: go to http://codeguys.rpc1.org/firmwares.html and download and run the patched firmware for the 811s. Your computer should then recognize your drive as an 811.
Step 2: go to http://codeguys.rpc1.org/utilities.html and download the EEPROM Utility for LiteOn Drives. Run that program and click on the "crossflash" tab and then on the button 4x1s->811s (drive). Once you do that, everything should show up as an 811s on your system.
PS, you may have to download WinAce in order to decompress the file.
PPS, Now that I think about it, it could be step 1 and step 2 were reversed, but I don't really think it matters.
Good luck, Rick