To me, you're question is not absolutely clear. If you are saying the patterns are 30% above and 70% below the point of careful aim, from a steady rest, flat down the rib, that appears to be a bit low. Before doing anything, though, I would pattern the gun at a measured 16 yards, standing up and firing as soon as you mount the gun. Shoot at least three shots with each barrel. Then if it still shoots low, decide what to do. The barrels could be bent up or you could raise the comb, as has been suggested. If your 30/70 means the pattern is 30% below and 70% above the point of aim, I would just float the targets a little higher. Bending the barrels would be my last choice.
