Thank you Bill and Dennis!
Bill, I hadn't thought about that much. Since you mention it, it may be good to put a removable panel on the front that hides the opening and tunnel portals on each end. More and more ideas!! 
Who needs a big layout? It is true, I will never finish this small one!
Dennis, I was able to do all this standing up with an extra high surface to support the wood when cutting, so I didn't have to bend over. I built a lot of the two stations and signal tower standing up, and will probably do the shingling, foundation, and other trim work mostly standing. Standing isn't bad; it's walking, laying down, and sitting that are the problems. I think I will get up from the computer chair now; it's starting to hurt. 
