I finished the patching of the back wall in preparation for the nice sky blue paint (suggested by Gayl Rotsching of Cincinnati). The walls were a mess and took two tubs of concrete patch to fill all the holes. They're a little lumpy, but better than holes. Next I'll put a coat of Behr concrete primer and then Behr one-coat concrete paint tinted a nice sky blue.
I patched just as far down as the railroad will be up so as to save labor and $$$. No one will see what's below that line and no one will care. It's all an illusion, isn't it?
I've marked the floor for the camera tripod so I can take time lapse photos from the same spot each time. It should be interesting to see it growing over the next several months.
The more I think about, I do think I'm going to use Clem's roll-away access door instead of the swing up door. It will be less expensive and less complicated.