So I want my game to draw to a specific "optimal" size and then be stretched to fit screens that are a different size. I'm using LibGDX and figured that I could just draw everything to a FrameBuffer and then resize that buffer to the appropriate size when drawing it to the actual display. However, my method does not work, it just results in a black screen with the top right quarter of the screen white.
Intermediary is the FBO, interMatrix is a Matrix4 object, and camera is an OrthographicCamera.

    @Override
public void render()
{
    // update actors
    currentStage.act();

    //render to intermediary buffer
    batch.setProjectionMatrix(interMatrix);

    intermediary.begin();
    batch.begin();

    currentStage.draw();

    batch.flush();
    intermediary.end();

    //resize to actual width and height
    Sprite s = new Sprite(intermediary.getColorBufferTexture());
    s.flip(true, false);

    batch.setProjectionMatrix(camera.combined);

    batch.draw(s.getTexture(), 0, 0, width, height);

    batch.end();
}

These are the constructors for the above mentioned objects (GAME_WIDTH and HEIGHT are the "optimal" settings, width and height are the actual sizes, which are the same when running on desktop). intermediary = new FrameBuffer(Format.RGBA8888, GAME_WIDTH, GAME_HEIGHT, false);

    interMatrix = new Matrix4();
    camera = new OrthographicCamera(width, height);

    interMatrix.setToOrtho2D(0, 0, GAME_WIDTH, GAME_HEIGHT);

Is there a better way of doing this or can is this a viable option and how do I fix what I have?