Just out of curiousity, what compression percentage you wouldn't dare to go under...I know it depends on what are we talking about here, "Dune" (the movie), or an interview with the last Titanic survivor, but still...?
I usually remove most streams and extras on a DVD to keep the compression above 70%, if possible.
I've backed up some multi-episode TV series discs at around 55% compression, and the copies look pretty good. I usually use Clone DVD2 or Nero.
You'll also see this advice all over the board--use good media and burn at a slower speed to avoid seeing pixels and freeze-ups. I set the speed at 4x on a 12x single layer burner.
Latest AnyDVD to rip > VOBB to blank the unwanted on a DVD > Shrink to compress > ImgBurn to burn = Never starting a thread asking how to backup a movie
