Which version of DVDFab are you using? Decryptor, Gold or Platinum? 18.104.22.168? Are you only interested in playing the DVD on your PC or would you like to play it in a DVD player?
Depending on your answers, you can try playing with the “Merge” feature. Although not a DVDFab product, what I did with my multi-disc movies was use DVD Decryptor which can rip a title into a single file and then use “copy /b disc1.vob + disc2.vob godfather2.vob” to merge the files. I then converted the VOB to a WMV for my XBox, so I don’t know if that causes any issues when played with a VOB player - I have had issues doing this where it corrupts some chapter information but it’s still a playable MPEG file.