Hi regenesis
I got your point but the problem here is that all the sections including slideshow / masthead are put inside a div tag called t4-content which is set with max-width: 1920px;
If you want it display fully, you can override this:
.t4-content {
max-width: initial !important;
}
Then if you want any section not show fully, you need to go to Layout settings of template and set fixed container for it:
