I for one am giddy as a schoolboy about this! Of all things I could have been looking for all this time and you post about doing a model of one of my all time memorable things! Ever since that song by Gordon Lightfoot, I've not only had a special place about that song, but once I learned that is was an actual ship, well, that was that. Now, I realize your images and ability to utilize images is limited, but if I can be of any help at all, just ask! I got one link you might want to look at, it's by a guy who has an EMT site and extensive history about the Lakes and also, several images and text on this very subject.
GreatLakes
I hope the pics there will help with the design process and I have to mention that the link I gave you is rather loaded with pics,so it might take a bit to load, but well worth the time waiting.IMO. I'm looking forward to your release and behind you on this project!
UPDATE: I just found a site soley dedicated the Fitz.
http://www.ssefo.com/ perhaps this also with help with your project. Also, check this out, it's a site for Great Lakes Maritime Institute,but has a really comprehensive online mag, with many drawings of the ship, and from what I can tell, from bow to tail and above and below deck.
http://www.glmi.org/fitz/story/default.htm