I just wired one of these up myself yesterday. A tip that I saw (and used) on the person's website that I based my wiring on was to tie a knot in the extension cord inside the box so that if the cord gets pulled, it's pulling against the knot rather than the screw terminals.
Gets kinda crowded in there if you do that though, so my green wire is the only one that has a wire nut. I joined my two whites and my two blacks into their respective screw terminals rather than pulling it off of a third short jumper like they suggest in the Ranco doc.
Anyway, I was glad to have found folks like yourself posting pictures of what works. It's a simple looking electrical diagram in their documentation, but I was second-guessing myself a little.