The board won't go into the hole-just the coils. Then the 2 tabs on the outside of the plenum squeeze the edges of the board to hold everything in place. You'll notice the board has kind of an hourglass shape;the narrow spots are to register the board in the tabs. As I said,it's a very tight fit,so you might have to reach back there and pry one tab outward while you push the board under it.
Not a fun job,but far from the worst one.
Speed
