What kind of shotgun is it Stan? Chrome lined suggests recent manufacture. If so, maybe the manufacturer would make it right. Considering you only have .008" of constriction to work with, I seriously doubt if you'd get to where you want to be by laterally honing the chokes, especially in a chrome lined bore.
Nobody mentioned the thought of weighing the cost of eccentric screw in chokes versus the cost of a strip and relay of the ribs, with a slight spreading of the barrels to regulate POI. Yours must be crossing at around 15 yards.
