Today I tried graphite levitation using the Forcefield 3/16" gold cubes.  The picture below shows my initial setup.

I used 6 attracting pairs with each pair repelling the adjacent one.  I could levitate 0.5mm leads with this setup, leaving about 0.5 mm of space to the magnet faces.  7mm leads didn't work as well, as one end tended to drag.  The lift field is clearly less than with the gold rod design.  Of course it would help if the magnets were closer together.

I wonder if they could be glued together, a la Chris's suggestion to turn a series of cubes into a long magnet?

Pencil Lead Summary

Chris' messages with photos and sketch.