I think we should give Manning some different looks from zone to man. Tough thing is our safeties have shown they are no good in helping over the top. A thing about playing zone against Manning though, if we can prevent him from releasing the ball within the first 2 seconds from snap, his decreased arm strength means the ball is in the air longer. This favors playing zone coverage because the DBs can make a break on the ball.
Think about this: in basketball, a good post player wants to keep a body on his defender so he knows where to position himself to make the catch on an inside pass. This can't be done against a zone in basketball because the zone defender player doesn't make contact with the guy inside. Similarly in football, the defender in man coverage (unless he has superb positioning) is a step behind the receiver and the receiver can position himself to make the ball impossible to get to. The DB has to go through the WR to have a chance at the ball.
This wouldn't work against all QB's, and not even Peyton in all circumstances. But in select spots, taking advantage of Peyton's decreased arm strength in zone would decrease some of that YAC.