I would like to have a susy grid layout like the one on http://www.mattk.com
To me it looks like 3 regions have a max-width and two that span the whole screen. Is there a way to have the container to have a max-width, but a couple regions go past that?
The simplest solution is to use multiple containers. Anything outside a container can span the full width, and anything inside can be aligned to the grid. In this case, the navigation and branding are in a container, but the hero image is not. The main content is, but the footer is not. Etc.