All Usabilla application page containers should use sb-container which is set to a max-width of 1920px.
If you want a Usabilla page to be the full window height (minus the header), you can use sb-container--full-height.
You can also use sb-container--full-width for full width containers.
And sb-container--sidepanel transitioning to sb-container--sidepanel-collapsed if you are using the sidepanel component. And sb-container--centered if you want to center a div that is smaller than the parent

Browser support: IE9+, Safari6+, Firefox30+, Chrome30+