I've got an LG brand burner, model:
HL-DT-ST DVDRAM GSA-4163B
It burns at around 1.4-1.8 times, despite the -speed=4 option.
Test iso 14th October
Media encoded burn rate
I read some where that the media has a track on one edge that gives the burn chariristics. I found the -burn speed to be a maxium setting not a minim. feeling ill today sorry for the misspellings. ah chooo