Your point about the difference between our models of articulated locomotives and the prototype provides an excellent reason to buy plastic articulated models rather than brass. The brass models are faithful to the prototype right down to the way they are articulated, with the rear driver set one a solid frame that includes everything from the cab forward except the pilot which is part of the front driver set sub frame. We have had people try to run brass Challengers, not Big Boys on our club's modular layout. Even with 36 inch radius curves, if the Challenger was on the inside main, the smoke box hung about 1/2 inch past the outside track on the outside main! We had to restrict them to the outside main, and then there could be no scenery items to the outside of any curve on the layout for the smoke boxes to hit! We have one old corner module that has the tracks running through a cut with real rocks embedded into the plaster on both sides to simulate outcroppings. If that corner was used, we could not run a brass Challenger on the layout. If we had tried, the damage would not have been to the layout, those rocks embedded in don't give at all!