Moulée St-Pie Inc. in Saint-Pie, Quebec, on old Montreal Maine & Atlantic defunct branch between Farnham and Ste-Rosalie (former CPR) is a great source of inspiration.
This small locality is served by 2 unusually located feedmill and elevator built in the middle of the town. One of them, the oldest, is built tightly against the mainline. This is what I'd like to reproduce on the layout.
The space between the building and the right of way limit is about 55 feets, thus 7-1/2" in HO. Walthers Farmers Coop elevator is about 4-1/4" deep, so it bring the total layout to about 12" wide. That means my earlier estimates were right.
On the prototype, a nice and tall hedge is growing along the track which could provide visual interest.
At this point, I consider I've planned enough the layout. No need to go further, only a real mock up with tracks, structures and freight cars will help me to find the best balance for this scene.