Wait a minute, you said this was not off the bench, but hand held. Before you start bending anything, go back and try this off the bench so you are not as likely to induce the flinch factor or some other variable. Then working off the bench, add moleskin to raise the comb, be careful about making the stock wider as you add height as that can change point of impact side to side. From the photos, it is hard to know just how far off in inches the pattern is, but 1/16" change at the face moves the pattern approx 1" at 16 yds. Once the bench point of impact is where you want it at 16 yds, (I like about 60% of my pattern above the point of aim so I can hold low and see the whole bird in flight) get off the bench and mount and shoot to find out if the dynamic shots are significantly different from the static bench shots. Adjust as necessary. One other point, you said all your guns are setup the same, but seldom are all guns matched with stock thickness at the comb/cheek contact point. It may be your problem is resolvable in a slight change in cast. So just be aware of that while making adjustments.
