I happened onto the following photo this morning, and am interested to see comments about form cues from the photos.
http://www.guardian.co.uk/sport/2013/apr/19/camp-mo-farah-london-marathon
To me, it is apparent that Levins is way off the ground, wasting time and energy in the air. His back foot is already well off the ground, while is front foot is not close to landing. Rupp's back foot has barely left the ground at toe off, and his front foot is much more advanced. Likewise, Levin's CofG is much higher in the aim.
I'm interested to see stop action sequences of Bekele vs Geb, and Viren vs Lopes, if anyone happens to have them.