2Cool has a great example of what you are trying to do. He uses IFOEdit and Decrypter to to split "The Matrix", removing the FBI warning and other stuff. He keeps the original menu on both discs and modifies it to work correctly for both discs. How well this would work for you would depend on your ability to apply the guide to other movies.
http://forum.doom9.org/showthread.php?s=&threadid=53458
It becomes a lot easier to do if you don't need to keep the menu. You can just reauthor to remove stuff and split the movie with Shrink, creating two ISOs, then burn them with Decrypter.
If I was doing this I would split and reauthor with Shrink then make menus for both using DVD Lab. You could even use NeroVision Express 2 to create a menu structure for each disc. I just like the great menus you can make with DVD Lab. It's got a 30 day free trial.
I had been splitting with Shrink and burning with Decrypter like you mention and then I upgraded to a DTS cabable Amp and found that since this method does not provide menus I could not choose the DTS sound track.
Is there a way to use the Shrink Split method without menus and utilize the DTS tracks that you know of?
Then you mention creating your own menu with this Lab.... I have not experimented with creating my own menus. Is it straight forward enough? I do not need to add another hour long step to my backup process. You know what I mean?
You can keep just the 5.1 audio with Shrink and get rid of the rest by checking/unchecking the appropriate boxes.
Making menus in DVD Lab is a long process because you have so many choices. For example, you can have multiple menus if you like, You can create your own backgrounds and even have motion menus. With DVD lab you can do any editing you may want to do.
There is quite a bit to learn, but once you get it figured out, its a lot of fun. You can do some pretty cool things with it. If you just need simple menus I'd go with something cheap from Nero, Ulead or Pinnacle.
If you get bored with just burning discs, an authoring program can be challenging and a lot of fun.
