Max size for renderer video bg screen?

Hello, For my iphone qcar app I wan't to take advantage of the retina displays and set my gl view content scale factor to 2. The problem is this creates a color render buffer backing store of 960 * 640. I create a VideoBackgroundConfig object with those same dimensions, however when I render it only shows the video screen taking up a small portion of the view. It looks like the default sizes for VideoBackgroundConfig are 480 * 360, it this also the max size, if not how can I make my video background screen larger? Thanks Brian