Acorn,

I used a subset of your reveal class here: https://initiostar.co.uk/demo/CSS-Reveal/ and all works as expected. Provided the Navbar elements are at the front (and in the correct order and top in the Page & Layer Gallery), I think everything slides under the stick-at-top elements without any additional code.

For completeness I ran Siran's code in my example here:https://initiostar.co.uk/demo/CSS-StickTop/

I think the only time the OPs issue would occur is where you have a link (MouseOver or Popup); not sure then that there is an alternative to using SaT z-index

The reveal approach was a great idea and thanks for sharing.

Gary