YES. I do this action . but a stereo audio plus ONE DD5.1.
Bill Hunt said a very rigth thing. If you want more than one DD5.1 aidio . use multiple Timelines with the same video and diferent audios.
Eg.: English 5.1
another for French 5.1
another fot Portuguese 5.1. In the main menu, you will have a dedicated Play Button for each one , or use the other method tha is audio selection, but i do not know how to set up this way.
Encore is smart enough to do this without repeat internally in the DVD the video file.
It reuse the video file in multiple timelines. The increase in size is only because the different audio files .
The other option is use Convert X do DVD, that supports 8 audio filies i think and up to 23 or 24 subtitles. for each video. But here led to the firsts discussions here about workflow. the quality will drop becouse anither reconvertion.
The tip from Bill is the rigth decision.
Best Regards,
LeoSSom.