I'm trying to get rid of the top title bar on a fullscreen-sized window under Gnome 3.12.2, using the gnome-shell WM. In earlier versions of Gnome this was not difficult to do, but it apparently has become impossible in recent versions. The "Maximus" extension doesn't work correctly for me (https://extensions.gnome.org/extension/354/maximus/); it makes the title bar narrower but doesn't remove it.
What are my options, if any, for making this work?