Soundtrack Pro: Have two audio tracks of the same performance, mono, one recorded L side of stage other R. How do I sync them into one Stereo L/R track.

So you have two independently recorded audio tracks and want to create a stereo pair? I'd like to know exactly how you recorded those without getting an audio pair off of the recorder? There is no automatic sync in STP. FCP X can do that, Plural Eyes can do that, but not STP. That said, you can do this manually in STP and it is not that difficult. Import both files into an STP Multitrack Project. Place on in track 1 panned left, one in track 2 panned right. You'll have to watch the waveforms here and zoom in close enough to see waveform details. Move only track 2 (do not touch track 1 at all) and visually match them up. Play them back and continue to manually adjust track 2 to match track 1. Move tiny, tiny amounts. You should get it matched pretty quickly. Then export as a Stereo AIFF file at 48kHz, 16-bit.