Adjust width for content block for a single page, independent of Site Styles/Site Spacing in 7.1

I have a site in 7.1 with an overall width I like in Site Styles/Site Spacing but use an embedded script in a code block that I'd like to span 100% of the browser window OR a larger px value in the Site Styles/Site Spacing site-wide settings. (Ideally, I'd like this to not affect the header or footer on the page, but if it did, that'd be OK.)

I just want it for this single page and can't find a way to break the page's content area container. It's not in the Format options for the content, as that limits me to the site space. 

Is there a place to force some CSS or other override for this single page? 

Can you share link to page where you have problem? We can check easier