I run 2 670 4gb in SLI at 5760x1080, i get a steady 60fps with the game maxed except i disable shadows completely and disable AA.
However there are still parts on most maps that fps will bomb to 35 fps, happens a lot looking down scopes and one map in particular seems to be 35fps in most areas (a town with a tower in center for snipers and grass around the edge.
Also noticed turning settings down further doesn't seem to help
game needs some patching for better performance.
So yeah, try disabling shadows at least, they seemed to cause the worst performance hit on my setup, also caused some pausing and stutter.