OK what I do is this. If the menu is small - say <50Mb I don't tinker. Otherwise use MenuShrink.
I put all my efforts into the flick - I figure I'm only gunna watch the extras once anyway. If there's room on the disk, I'll pop some extras on, but no biggie - the original DVD can be used to see the extras.
Try to keep your main movie above 3500Mbps (using the FHE high-high matrix). At that level even the biggest projection screen will play it flawlessly. Higher BR if possible of course. Cut the credits ruthlessly if you don't need them. I like to turn the cast into 15 second stills (say 3 stills, saving about 200Mb) - see here.
If you've got the movie in at 100% and wanna add some extras (Hitch R4 was a good example), then make it 100% movie and lower the BR on the extras. I run it in Half D1 and used robot1's RBOpt to make the extras at about 2300Mbps. Not bad, and Procoder smoothed it nicely. Of course, this took some tweaking. I had to remove the movie (with PgcEdit), figure out my new target sectors left for the extras, fix rebuilder.ini, set the right BR for the extras to fit, encode and replace the original movie (uncompressed). Took a bit of work, but it came out a dandy.
Now, here's the rub. With DVD Shrink, it is so easy to implement this. You can keep the movie uncompressed and the BR for the extras will go down accordingly. But.... as a transcoder, the quality will just suck. So you need to re-encode properly, unless you just got a TV (say 68cm) where it won't be noticed.
Ummm... why is this discussion happening in this forum and not at d9?
Regards