even if you don't have the electronic view finder, at least put a corner against your forehead. 3 anchor points will always work better then just 2
3 = both hands and head
2 = just 2 hands
walls are acceptable alternatives to a head, and sometimes preferred as they don't rock
also depending how you hold NEX-5N change holding to one hand on camera body and one to lens, gives a stagger and spreads the weight of the unit for more stability.