Moving to Sections - 3 columns don't fill width of display

I am moving to the new Sections (and have to say it is making my life a lot easier so thank you and kudos to the developers).

My minor issue is that in my old 3 column layout before, the columns filled the entire width of my display. I had carefully designed the front end in to a rectungle that filled my touch screen.

With sections there is a perfect rectangle as designed, but it is too small in all dimensions. Everthing works but there is a big gutter all the way around.

The work around is to zoom the browser in by 25% but is there a canonical way? I notice that if I disable

.container max-width

when I inspect the css this has the desired effect. I am not sure how I would disable that correctly though.