My thinking is this:
An increase in CS size will result in increased depth (distance from top to bottom) only. And an increase in the size of the two CC’s will result an increase in the left to right width of the shaft. The latter scenario would also effect the average depth of the shaft, but not the maximum depth (as this would always be determined by the CS, as it is the lowest point of the shaft).
What is interesting, is that for a given increase in the diameter of the cylindrical CC’s, the increase in shaft width will be twice this (The shaft width is basically made up of the combined diameter of the two CC’s). Perhaps this is why some people find that the more they PE, the less round their shaft becomes. I have certainly found this, and so need to work on my CS chamber.