If you want to have the same field of view (FOV) of the player’s camera, then you have to change the distance between the DefaultViewPoint and the screens inside your nDisplay config. Also, if you want to each viewport render the same image, then you have to position them at the same location inside your nDisplay config.
Here is the nDisplay dual monitor template, but with the two screens positioned at the same location (you will only see one screen, but there is two at the same location)
Here is the result.
