Did some toodling on my own.
You can pull the NSArrayController from the palette and then switch to instance pane, subclass it and then have inspector identify it as the custom class for the IB instantiated object set and then create files.
So, I got some connections from a broader map of experience of Mike Beam articles than merely following Mike Beam's current article (I was brave and tapped into my own mind).
It was very fast on a G5 with dual processors to fiddle like this.
I suppose overrides and actions and outlets all require subclasses so you can create code. This article exhibited closure and demonstrated that you didn't have to create any code, but by toodling, I found I could and hadn't lost "that world", but remained open to it.