The carrier barrel my friend has is very light and cannot be shot without the tubes in it. However, the assembled carrier barrel and tube set weigh slightly more than the 12g barrel he has. I see no reason why a heavier 12g barrel couldn't be fitted or even some weight added to the 12g barrel to bring it to a perfect match.
Me? I've had two tubed guns that were not "carrier barrel" setups. I couldn't swing ten pounds of K80 or 3200 to catch a bird. So, for the K80 at least, I bought 3 other subgauge barrels of matching weight. I loved it. I dunno how all these people can shoot those 9 and 10 pound monsters with tubes, but it seems they can and even smaller people than I shoot them well. But I bet that's why they don't shoot well in adverse conditions when the birds don't fly as predicted also. I like my 7 3/4 lb 32" 682 that balances very forward. It's quick yet has very good swing inertia. I noted that Perazzi is lately offering a gun/barrel (32 or 34") combination very much like my 682, maybe lighter.
