Thanks for the reference pictures zathros, but mine is based on the wooden model you can buy if your willing to spend $150-$200. The engine will look close to this one.
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The actual engine is located under the curved piece of metal on that Wooden model, towards the stern, under that curved section is a two cylinder steam engine (which was a dummy engine , in the movie, but accurate nevertheless). I was showing you the engine how it looks exposed. They covered them as they got very hot, and it was bad enough to touch the cover by accident, than boiling a hole into you leg! I don't know the overall length of your model but a small minimalist representation of the engine would be a nice touch. Using thick gauge copper wires, you could simulate the piping.
Lofting Hulls is something I learned many decades ago. The African Queen had a wide entry into the water, then narrowed slightly towards the stern. Yours is close enough, and if you ever saw that movie, "The Four Feathers" I have a paper model of the Steamship they dragged up the river to shell the fortress! P.M. me. It's similar to the B&W picture below.
HMS Gunboat Heron (They used Army artillery on the decks on these ships which could then be off loaded for land use):
You can download these movie for FREE on YouTube, it is an incredible movie all shot on location.