Hmmm, shall have to think more about this ... my first reaction would be 1. .. f9-f8, my memory tells me both d1-d5 and d1-d7 tend to lead to losing positions but not with the white response 2. e5-e4. If you assume 1. d5-d8 f9-f8 2. e5-d5 then I guess d1-d2 is required to end up with the 5 open squares for the white King as you say. Shall have to try this out in a couple of games and see how it pans out. I think the trump is the white pawn at c5 which white would want to lose to open up even further this side of the board and black will be hard pressed to not capture it.