Adam,
I have a few little nits to pick, but I think it is looking good. I think you have the right proportions and
things are fitting onto the mechanism right, so it's going to work.
The walkway looks high because it is arching up in the middle right now and that makes
the boiler look a little high.
When you straighten the center "bow" out of the walkway, I think the height proportions will be right, just basing this on eyeballing your model photos and the prototype photo you showed. Look at where the end of your walkway sits over the cylinders, and how that utility box has to fit in there between the top of the cylinder and the underside of the walkway. I think you have it just about right.
When you add some appliances, like the power reverse under the walkway, that will help to visually close
up that space down to the drivers.
One thing to do see that you might want to work on:
The joint between the added boiler section and the smokebox section (where it goes from black to silver on your model)
looks like it is flaring out a little at the joint with the silver part. A little sanding there with a piece of sandpaper
wrapped around the joint would straighten that out. The prototype looks really straight through there, like
the barrel of a gun, so it would be good to preserve that look.
I think this is coming along nicely.
