Bbscout,
5 degrees up is certainly well in between 17 degrees down and 40 degrees up. The article certainly doesn't disagree with that part of your statement and to a great degree supports it. I didn't look to see where the optimum distance below center was but it wouldn't surprise me if it wasn't just about 1/2". I was disagreeing with the last sentence replying to Rocket. Based on the article it doesn't make much difference if you hit the ball with a level swing or a 5 degree upswing and based on the graphics that Sandman posted I'm guessing that when Williams pulled those inside pitches into the bleachers he was making contact during a part of his swing where the angle was more up than 5 degrees. Williams was more in tune with the reality of the swing than anyone else, but if he was playing today and hadn't published his book he'd be considered a player with a very "level" swing.