Squarespace 7.1 Centered Navigation Width

To prevent a centered navigation on Squarespace 7.1 wrapping into multiple lines on wide enough screens, add the following code to the Custom CSS field:

.header-title-nav-wrapper {
  flex:1 0 80%
}
.header-layout-nav-center .header-nav {
  width:100% !important;
  flex:1 1 100%
}