Ok I had some old prodisc I did not mind wasting so I took a vob file from an next generations disk and moved it to another folder on my hardrive then removed the first vob file form a voyager dvd to another folder on the hardrive I then went back and renamed the next generations vob file to VTS_3_1.vob which was the same as the one I had removed from voyager. The reason I had to rename it was the next generations vob for the movie were _2_1 and so on while in voyager they were _3_1 and so on. I then place the renamed vob in the voyager folder to replace the one that I had removed. I then burnt the disk I then burnt the disk using clonedvd2. I then played the disk and when I picked the first episode on the disk for voyager I got the next generations episode that I had placed in the disk to replace the vob file that should have been used. The sound and everything was next generations sound.
Both the next generations and voyager disk I had on the hardrive were already ran through rebuilder to shink them and I did not have to rerun it before burning.
I just could not help myself I just had to test it again to see if it works and it does so have fun mix movies up all you want.
The reason I learned how to do this was I had a disk that was so bad that dvdshink or any other program would not let me back it up and since the Vob file that it was having problem with was in the extras I just copied the rest of the disk to the hardrive then took a vob from another movie and used it to replace the one that was bad then I just burnt the disk and did not worry that if someone went to the extras they would see something that should not be there.