locomotive c57 180 by canon

Good work so far, I want to see more, sir. :)
About the round windows (or other holes required in card models) - I have bought a set of hollow punches, they can do good round holes or wheels. There's nothing new, it's an old idea and it's not mine.
Another way to finish a round window/hole is to use a round file smaller than the hole.
 
Coming along nicely! It really is big!! ;)