I’ve scratchbuilt a number of RC boats including a model of a modest Great Lakes Freighter complete with a plum bow and a counter stern. Scaled to HO, it is about four feet in length. The hull construction is a series of model aircraft plywood bulkhead (ribs) placed on 2" centers on a backbone of ¼" square stripwood planks with a protruding stripwood keel.
To get the proper hull curvature, you have to design in “datum tabs” at the top of each bulkhead. Think of the finished hull as being placed upside down on a flat surface, the datum tab will be the distance from the flat surface to the top (deck level) of each bulkhead. Actually, this is how you build the hull - upside down on a flat board. When the ribs are planked, you cut it loose from the flat surface and cut off the datum tabs.
As boats go, G-L freighters are easy to build because with straight sides, most of the bulkheads are (almost) the same. This allows you to cut a sandwich of bulkheads at one time on a scroll saw (a very good investment for this project).
I used scribed Northeastern siding as hull plating (scribed side facing to the inside). For complex curves, I used blocks of balsa, cut and sanded to shape. Coat the inside with fiberglass resin (in a well ventilated area!) this adds stiffness to the scribed wood which helps in the next step. Then tackle the outside of the hull by applying a coat of resin, sand… apply again and sand…repeat…repeat…repeat; until you’re happy with the look. From there you build the superstructure and add the details. For steel, styrene would be a good choice.
My Great Lakes Freighter was built in the late 70’s, has logged many a nautical mile in lakes and ponds and is as seaworthy as the day she was launched.
Other responders have noted the size that the Fitz would be in HO, and this could be an issue for most train layouts. However, you could build a portion of the bo