Minor motion tracking for 2 second shot of big screen

I have a 2 second piece of footage of a big outdoor television screen. In the footage I have, the screen is displaying an image that I don't want to use, so I've masked in a different, static image over the top. This has worked pretty well, but, although I have warp stabilised the original footage, there is still a very small amount of camera shake. And the masked layer does not move in tandem. I would like you to adjust the masked layer so that it moves in sync with the original footage so it is seamless. Here's a couple of images of the project: [login to view URL] I've uploaded the AE CC 2014 project and the necessary files to Dropbox, here's the link: [login to view URL] Samples would be great!