Looks good. I have two of these, but I didn't use any boxes. I cut a hole in the fridge door, mounted the temp controller in the door and ran the power in/out, out through the door gasket. I also tape the temp controller to the outside of the fermenters as soon as I put them in. Not sure why anyone would ever want to measure any other temperature inside the fridge, than the temperature of the fermenting wort. I didn't add fans, and I think I get a pretty damned even temp in the fridge, as the temp controller is taped onto the top ferment, way down low, about in the middle of the fridge.
My total cost for a Pigeon Pair fridge and freezer, two temp controllers, two five meter cords, two light fittings, and 2 big bulbs, was $250. I might still look into the fans.... we'll see how they go.