A two camera set-up won't work with FaceRig. To expand on this, consider that there are two cameras connected to your PC. Launching FaceRig will use one of the cameras exclusively, and that camera won't be available to be used by other applications. There is only one web-camera tracker available in FaceRig, so two cameras cannot be connected and used.

Darn. I wanted to see if I could use two since I have a huge computer screen which means I cannot put my camera near the center. So facerig interprets my face angle and expressions to wild degrees sometimes.