Either your digram is in error or I just don't understand it. However, it seems to me that your bookcase top and bottom portions are not parallel with the shelves. I had the same problem, but I didn't want to drill holes into the wood paneling on the wall to secure the bookcase, so I built the entire bookcase to lean against the wall. This means that the bottom panel, the foundation panel (the panel that touches the floor) of the bookcase is connected to the vertical supports AT AN ANGLE, the same angle as all of the shelves. In other words (I find this difficult to explain), all horizontal panels are parallel with the floor, but the vertical panels and supports are at an angle to the floor. This confused me during its construction an embarrassing number of times, but I finally got it right. Anyway, the only thing I would change if I did it again, would be to use lighter vertical construction. My bookcase has seven shelves and contains many very heavy books, so I made it too strong. If I did it again, it would look less like a battleship. [The top shelf rests against the wall and the bottom shelf is 6-1/2" from the wall. The bookcase is 83" high]
