I will try to answer all your questions in one message. First off thank all of you for your kind words. It is really special when other model builders appreciate your work.
The engine will run on steam or air either one. I always run it on air because it is a lot cleaner and easier. This model is 1/20 scale the original had a 15 foot flywheel which translates to 9 inches on the model. The real one was built in the 1800's and at the end of it's useful life it was used in a textile mill in Texas. The main difference in building something like this and building a scale model plane is that you don't have to worry about the weight of a steam engine. This one probably weighs 25-30 ponds with the wood base.
I used to build scale model planes and may give it another try as my next project. If any of you ever get a chance to visit a "model engineer" show such as the one they hold every year in Toledo I am sure you would enjoy it. There you will see such things such as 9 and 18 cylinder scale model radial engines that are about 12 inches in diameter. They actually run. Ever see three real Morton M5's and three reproduction ones at the same time? Last year a man had a couple of non flying model planes there one of them was an SE5A with no covering. It had every gusset, cable and turn buckle to scale. The stick and rudders actually worked as per the real one.
Oh yes I have been to Greenfield Village but they didn't have anything running when I was there.
More to the subject of CL models. I have my Flite Streak finished and I have set up a flying date for weekend after next. It has been 35 years so wish me luck. I am not worried about keeping it in the air as much as I am about getting dizzy. (A lot of people think that I am already). If I balance it as per the instructions it is going to require quite a bit of weight in the tail. This makes me a little nervous because I once flew a 54 inch wing span J3 Cub that was tail heavy and it wasn't a pretty sight, but that's a story for a different time.
A lot of things have changed in the last 35 years, but I found out at St Louis, CL flyers are still a great bunch.