Changes in dimension can be documented accurately by consistently measuring to the bottom bracket spindle. It is more accurate to measure to the bottom bracket spindle because of the pedals tendancy to move. The length of the crankarm is consistent and not effected by any of the changes in adjustment. It can be difficult to define the TOP of a saddle. A reliable method is to measure to a straight edge that has been placed lengthways on the saddle from the tip to the tail.
Most saddles are actually lower in the middle.
Please remember that any measurement is only useful when comparing to another. For best results choose the points you wish to measure to and remain consistent. The rules Let us start by saying that we are pretty sure that there are no rules to saddle height adjustment. In our experience we have seen many successful riders use very different approaches to bike fit. Different saddle heights suit different riders.