In the latests Alpha 2 the Fullscreen positioning doesn't work properly. Whe you open a page this is the behavior:

iPhone: When you open the page the header/footer are hidden. When you tap nothing happens. When you tap again (2nd try) header/footer are displayed. At this point, everything works properly.

Android: Exactly the same as the iPhone.

Desktop: When you open the page the header/footer are hidden. When you click again header/footer are displayed. Also, if you move the scroll bar, header/footer are displayed too.