It could be any # hangar. Whatever it came from the factory with was what it took to shoot parallel(spelling). You will have to shoot it on the bench to find out. I would guess it came with a #4 as that is what most of them take to shoot the same both barrels. Krieghoff has a trade program if you are interested. Be aware that choke tube and fixed choke have different hangars. Hope this helps a little.
Initially I thought that having the bottom barrel shoot high was a good thing, but have since changed my mind. I figure that if everything hits the same spot its got to be easier on the 'targeting computer'.
I've got the unsingle set to match the under barrel's POI, and it's one line above the '0'. The manual shows one line=5" and each # increase on the hanger=2.5", so I figure 3 must be about right.
I'll call Ottsville and see if they'll swap hangers for me.