Help needed, Autohide toolbox but the top gets cut off

I'm using MrOtherGuy's autohide_toolbox.css code it's excellent, but like 4 vertical pixels are gone at the top above the tabs, tried using this code, top doesn't get cut off but it doesn't hide the Bookmarks Toolbar while the setting of Always Shown is on, any help please.

Here's the comparison photos not edited open the 4k overscan test pattern in a separate window to display it correctly