So I built it and it fits!
I tried taking your advice as much as I could.
I used TV riser B so I wouldn't have to buy more wood, glued the pieces together, screwed three #10 2" screws down vertically on each side, used 4 L-brackets about an 1-1/2" in with 4 #8 3/4" screws in each one. Then, there was a 2-2-1/2" piece that was as long as the entire thing, so I glued it to the back and screwed it in with 6 #10 2" screws. This piece was screwed into the feet and into the top board, and acted as a skirt/brace/lip. The glue was liquid nails.
The damn thing is solid and fits almost perfectly!
Now I just need to figure out how to cover it with a black fabric and figure out where to buy that fabric!