Screen passes work when the defense is pinning its ears back and rushing hard. Since the 49ers play a power game featuring many runs and high percentage plays we haven't had a ton of situations where defensive ends have over-committed. CK is such a dangerous weapon outside the pocket that even though they are rushing, defenders have been paying MUCH better attention to not being so aggressive and thus are staying home a bit more than they were against Smith. Although screens can be effective at the right time, these factors make it a lower % play than it would be for say the Green Bay Packers.
Scheme-wise, the pistol formation for us really is about the run, run-option, and play action. Defenses counter this by stacking the box, spreading out the LB's and paying more attention to staying in their gaps. Not an optimal scenario for the screens.
[ Edited by bzborow1 on Dec 31, 2012 at 8:19 AM ]