Maybe if you mentioned the movie, or search for it in the forums?
Firstly, use DVD Decrypter to rip in file mode. see how big files are originally?
If you can live with the movie only, no menues and bonus/extra/previews, try re-author in DVD Shrink. Pay attention to the audio. You may have large audio streams you do not need. Also, maybe there are 2 versions? like WS and FS, or director cut, etc
If after all this the main movie by itself is still too big after maximum compression, you might run the files again in DVD Shrink. In this case you will see lost of sharpness. This second shrinking might work mostly for slow moving, well lit, episode TV shows,