Maybe someone can help me with my issue with Sony Vegas:

When I started my Star Wars edit projects in the past I used a stereo source. So my whole cuts are only with this one track.
Now I want to replace the source with an 5.1 file… but when I replace it by Sony Vegas, then only one of the 5.1 tracks will be used because my project have only one audio track.

I changed the project settings to 5.1 and I added additional empty audio tracks. But only the already used track will be replaced.

Does someone has an idea how I can replace my stereo project with 5.1 source without repeating all cuts with the new source?