Change widget bar size

Hi there, looking at the CSS and HTML on your site, at screen widths of 65em and wider, the sidebar is right at 300px (18.9em). Below 65em and down to the point that the site changes to a single column, the width of the sidebar is around 240px (14.79em). The reason for the drop in size is to keep your content prominent and readable for your visitors. The following will keep the sidebar at 300px in width clear down to 51em in width.

@media screen and (max-width: 65em) and (min-width: 51.0001em) {
  .site-header {
    width: 300px;
  }
  .site-content {
    max-width: 56% !important;
    width: calc(100% - 300px) !important;
  }
}

THANKS!