newtonian mechanics - Hanging a brick free over an edge by stacking them

National Geographics TV has a series called "None of the above". In one episode the presenter shows that by stacking 4 bricks (here shown as 'xxxxxxxx') you can have one of the bricks completely hang free of the edge:

           xxxxxxxx
       xxxxxxxx
     xxxxxxxx

    xxxxxxxx
 [edgeedge]
 [edgeedge]

It barely hangs free, but it does work if you are careful. I have found a more efficient way also using only 4 bricks:

        xxxxxxxx
   xxxxxxxx  xxxxxxxx
       xxxxxxxx
 [edgeedge]
 [edgeedge]

This will let the brick be much further out. This gets me to think: Is there an even more efficient method - either using fewer bricks or a different way of stacking to shift the brick even further out? How do I compute the optimal shift lengths of each brick?

Edit:

After a few more experimentations it seems the optimal is symmetrical:

        xxxxxxxx
   xxxxxxxx  xxxxxxxx
        xxxxxxxx
  [edgeedge]
  [edgeedge]

The lower brick will be at 50% over the edge. The two middle bricks will be pulled as far out as they can before they drop. So the hard part seems to be computing how far it can be pulled out. Experimentally it is around 1/3.