Comment 8 for bug 489528

I've been brainstorming about this, and I came up with a mockup that removes the empty space, and changes a few other things. I moved the drop down options (Source and Type) to the top of the main screen, shortened their names, and those of some toolbar items.

If you don't like it, then other ideas: what about moving Source and Type to a Preferences menu, and moving the Zoom option to the View menu, leaving the document the entire main screen (minus menus and toolbar?).