Recently I bought a used multibarrel set. Though I didn't have them in my hands for long here's what I found.

The Krieghoff rifle was build as a Big 5 Classic and so the 470 barrels belong to the gun. The gun seemed tip heavy which Krieghoff says would be corrected by installing the 14 oz recoil reducer in the stock. The 9.3x74R barrels which came with the gun and carry the same serial number balance perfectly and swing fine. It comes up well. Now what will happen to that if the Breako is installed. They said it will still be fine. The gun also had a set of 7x65R barrels an after thought as it has a different serial number. It swings fine maybe a touch light but fine.
My son loved the way that particular set of barrels shouldered. I think if I install the Breako I might have to remove it for this set of barrels or else it might swing like a shotgun not to bad though. It didn't come with nor did I order the shotgun barrels yet but they sure as hell would be cool. Any slight handling problems with them I'll deal with if I like the gun.
I always have liked kits, things packages together to do multiple things. This gun struck my fancy and I liked it. I hope it lives up to my expectations. Time will tell.