On my 22 Foot TT it has 3 ducts. One right by the furnace and 2 at each end of the camper. By removing drawers and a couple of panels I can see all the ducts. It blows most of the air out of the duct near the furnace. This makes since if you think about it. That duct is closer and has the shortest distance and the least resistance to air flow. If your furnace is keeping the TT warm I would not start cutting anything. If it works don't mess with it.
Now, on the other hand, if next winter you are having problems you may have to fix it like the other members above have said. But, don't cut anything just yet. Wait until it gets cold and see how well it works.
