Hello Jameskoster, thanks for taking the time to reply!
I discovered that this will do what I want through trial and error. However, it is also affecting the main navigation menu (stretching it to full width, which looks awkward). I would like the main menu to remain about 65em wide, but it appears that the col-full class is a parent class.
Here is what I have in my child theme’s style.css now, it does not work for holdinig the site-header to 65em though.
.page-id-128 .col-full{
max-width: 100%;
margin-left: auto;
margin-right: auto; }
.page-id-128 .site-header {
max-width: 65.141em;
}
Any advice? I was looking at using a :not() in the first string to try to exclude site-header and all that stuff, but that did not work either.
Thank you!