Sticky masthead covers header titles

[WizardCell]

Hey Ben, long time no see!

When I press any of the titles inside the sidebar table of contents, the page scrolls past the title, or more realistically the masthead covers the header title.

The "fix" you already have in place doesn't work, which is this:

h1, h2, h3, h4, h5, h6 {
    scroll-margin-top: 5em; // This means it will skip the header

I found the real fix here.

Of course we can't just use the hardcoded 75px value, although it works nice for me. I'm trying to figure out how to use the masthead height instead, but I'm not sure how to do so. Please let me know if you figure it out :)