I only found 1 way to split a disc so it could be put back together.
1 Rip the movie using DVD Decrypter in file mode
2. Open Nero Express and choose DVD-Video Files
3. Click Add and add all the files from the rip (yes it will be too big)
4. Locate the largest set of .VOB files (this is the main movie)
5. Starting with the highest numbered .VOB in the set remove them 1 at a time untill whats left fits on a disc
6. Burn the disc and ignore the warnings and errors
7. Take the .VOB files you removed in step 5 and put them in another folder
8. Rename the .VOB files in order starting with VTS_01_1.VOB, VTS_01_2.VOB and so on
9. Use IfoEdit to create .IFO files for the .VOBs (IfoEdit is free, just google it)
10. Burn that onto the 2nd disc
When you get to the end of the first disc it suddenly will go to a menu, pop the 2nd disc in and continue watching. If you want to rebuild the entire DVD to burn to a DL DVD or whatever it is pretty easy. Just pop in the 1st disk, drag and drop the VIDEO_TS folder to somewhere on your hard drive. Put the 2nd disc in and copy just the .VOB files into the VIDEO_TS folder from the first disc. Then you have a fully rebuilt movie.