Full width header

I’d like to have a header with logo and navigation set to full width, like your example: http://blueowlcreative.com/wp/fortuna/ but I can only seem to get this to be boxed to 1200px

In the Fortuna Theme Options, this is set to Full Width and then on the page itself this is set to Default, set in theme options.

How do i set it so that the header content is full width?

Cheers