Can you do it?

This is an original SolMan game.  I wanted to make a series of games that progressively become harder.  I settled on Pairs, a simple looking game with deceptive depth to it.  Just pick off matching pairs of cards (if only it were that easy).  The hard part is deciding when to fill the table, as only one card may be in a slot.  Pairs_at_9 is pretty easy; so work your way down to Pairs_at_4, which is harder.  This one is insanely hard.