Hi Pete, I think the key is to ensure that vertical lines remain vertical in your photograph. That is the advantage of a PC lens, it provides you the opportunity to frame your composition without tilting the camera back. If the the vertical lines are straight, you did it right. I'm not familiar with any need to adjust the camera back to compensate for this. I aim to get the camera back (film plane) level at all times, when vertical lines are an issue. Just my 2 cents...