In the audio configuration page there is no option for 5.1 channel audio.
I tried to do a test with 5.1 audio, but only the options 1 channel and 2 channels appears, even though the Vegas project properties are set to 5.1 channels and the Voukoder template is set to (Use Project Settings).
Apparently it is only possible to render mono and stereo audio in this version of Voukoder in Vegas Pro.
In previous versions of voukoder there was no "audio configuration page", but it was possible to render 5.1 audio just by setting the project properties of Vegas to 5.1 in audio section , and voukoder automatically applied the project properties to the rendered video.