keep in mind that you're attempting to copy a DVD-18 (ie it's dual layered on BOTH sides)
if you attempt to compy this to a single layer dvd you're compressing to about 25% assuming each side of the flipper is full of data. I wouldn't recommend this!
if you copy it to a DL disc and you pick and choose what to include you may get acceptable compression.
the TV series House M.D. is also set up like this. I simply used 2 SL discs for each disc of the series when I backed mine up.