You could try using the Skew modifier applied to the camera for this, depending on the axis you choose it'll 'move' the backplate by skewing the camera space... however, it probably won't work if you use tilt/shift or distortion on your camera.
There's also the 'overscan' script, look it up on scriptspot, which extends the frame and changes the camera's focal length accordingly. This will probably not work on Corona Cameras, you'd need to set up a standard camera with the same position/rotation/properties and then use the script.