One requirement on this structure was that it be possible to pick it up to retrieve derailed cars inside, or on the staging track that passes beneath it at the rear. The stock kit builds into a compact rectangular box, which would be no problem. My version has two wings, with a big split in the floor where the track goes, which made worry that picking it up would put a strain on the middle of the building. So I ran two pieces of aluminum stock across to create a rigid spine, as seen here:

All the kit-supplied walls are now in place, plus the big back wall.The two right-hand side walls are scratch made by laminating generic brick sheet to styrene (the bond pattern is different, but not such that anyone will notice in N scale).

Build threads shouldn't always be tales of straightforward triumph; they should also record the Oops! moments, and how you solved them. Oops #1 is that the upper wall warped:

That's *not* going to make a clean corner. Fixed by gluing (Liquisilk) a short bit of aluminum channel stock to the back, and clamping in a bench vise overnight until the adhesive was good and cured.

Oops #2 is that I managed to twist the front lower wall a bit when attaching it to the base, so it's not quite vertical at that corner:

This one I decided to live with, as that corner is virtually invisible when installed in place:

The big pink block in the middle represents a scratch-built two-track chemicals and additives unloading building, with the kit tanks on the roof.  The stuff in the corner is a rough blocking-in of the main mill which is mostly "in the backdrop" (to be scratch-built). It's connected to the shipping building by an upper-level bridge, with a track passing beneath it, just because I thought it would look cool. Further right is the mock-up of the kraft mill, currently falling apart .

To do:

1. Attach those side walls, and also strips of brick sheet on the back of the parapets on the scratch-built walls.
2. Cut and install roofing sheets (to be enhanced with fine sandpaper), with HVAC details.
3. Play with interior lighting to see what I like.
4. Build and install occupancy sensors for the loading track (same as I did for the transfer terminal).