In many of Apple's Full Screen apps the UI components at the top of the window slide down with the menu bar when it slides on screen so that they dont get obscured when the menu appears.
This is useful when you move the mouse slightly too far and the menu pops making you wait for it to go away before you can select the tab you want.
Mail.app does it well, you could look at that for reference. It looks like the top UI components are anchored to the menu bar.
Customer support service by UserEcho