No Sidebar (Content Width)

Hi... I've chosen "No Sidebar (Content Width)" for a page in which I want the primary content to expand the full width of the site. But instead of doing that, the content box just centers on the page and is only partial width. I'd expect such a setting to stretch that content full width. Am I missing something? Here's the page I want full width: http://members.nippc.org/member-list/ Help! :-)