[BerntR]

His explanation about spine tilt was confusing at best. I read/heard Plummer and Bennet explain the side bend so I knew where Martin was headed but his explanation has me still trying to figure out what he was saying.

As far as I can see, Martin Hall's explanation about side bending isn't in the S&T book. Plummer and Bennet basically talks about tilting. Tilting and side bending isn't the same.