How to know which streams to join

Question

I'm ripping dvds using a series of calls like mplayer -dumpfile foo$i.vob -dumpstream dvd://$i. and using lsdvd to list the available streams to rip. Here is an example command I wrote for this

for i in $(lsdvd 2>&1 | egrep "^Title" | sed -e 's|Title: \(..\).*|\1|g'); 
  do mplayer -dumpfile foo$i.vob -dumpstream dvd://$i; 
done

To join the vobs together - UPDATE apparently this has been asked on superuser before, here.

Question(s):

1. Am I getting too many vob's? DVD's are regularly dumping 13G of data, seems twice as such as I should be getting.
2. Are the #'s of the vobs (as the command above indicates) in the correct order? Say, for example, for a movie? Can I just merge 1 followed by 2, followed by 3, etc?

Do you recommend a better way to do this (using command line tools for linux, and open source)?