I have been following this thread with some interest, and I agree with Mr. Roberts' inquiry above, re: stock dimensions.

I have owned a number of 21s of all gauges ever offered by New Haven and never found them to be what I consider "high shooting"
I include several TRAP specific 12 bores most with factory vent ribs , but also a couple of standard matted rib Traps, and never seen a 21 place patterns this high unless after market barrel bending procedures had been undertaken.

It is widely known by double gun trap and pigeon fans that the 21 Traps seldom shoot more than 3 inches high in factory issue condition.