Page templates in Marketpress

Hey, I'm excited to be getting started with Marketpress! I see that only one page is created and customisable for Marketpress, so how would I apply page themes to other Marketpress pages such as the cart? At this moment I'd like to make the cart page full width to reduce distraction when checking out but I can't choose a page template for this as the page itself doesn't exist. Any help would be great.

So far I'm really enjoying all WPMU has to offer!

Thanks heaps!