Creating Bluray Audio Demo Disc - Questions

[kevinokev]

Hey Bluray.com members! I would like to make a High Def audio demo disc using end credit audio exclusively. I have been successful in making a Bluray demo disc with both High Def video and audio (output as individual .m2ts files) and then authored.

My next project is to see if I can create an audio only High Def demo disc (BD25 with DTS-MA and TrueHD formatted audio). My questions are:
What extension should the end file be for each clip when I strip out the video and trim down the file to just be the end credits ?
Do I need it to be an m2ts file or is that specific to audio and video?

Please share your thoughts or include you own questions you may have for my process. I'd like to avoid having 7+ minutes of video for each clip if I don't have to, as that will obviously take up much more disc space per file.