5.5x5.75in for a standard CD Jewel Case, even with the "vertical" Playstatation bar, I would assume it's easier to convert a cover to a horizontal cover than a vertical, as there is less skewing of the image that way.
I mean, we're already messing the initial dimensions up, but considering how much farther you skew the Height vs Width on a veritcal compared to a horizontal IMO adds up.