It feels quite crowded what with the giant header following me around. I'm wondering if it could be either downsized or eliminated? All of my work is done from a MacBook Air, and the header currently takes up about a quarter of my browser's screen estate. In my mind most people understand that scrolling up will lead them back to the header - my preferred solution would be to lock it in-place up top.
Simple solution. You need to buy a new MacBook. 
I agree should it not hover. It should go away as you scroll down.