Mark Payne described the problem and solution some time back:
http://markpayneblog.blogspot.com/
after going thru this one time, I solved it more permanently with an Onpoint chassis. (which uses the AE 12R5 pivot)
the 12R5 pivot balls also help with alignment of the main chassis plate and pod plate. (the S120 balls were too tall, leaving the pod plate low compared to the main chassis)