Hi Katherine
I make no claims to be an expert in Egyptology (I'm not). However, I have conducted my own research which may or may not be of interest. Manetho may have used a very simple model to construct his chronology. It appears to work throught the period of time from late 5th Dyansty to the death of Cleopatra (last event after Manetho). My problem is that it is difficult to find convincing evidence that Manetho was doing something new or simply using information available to him. In my opinion Manetho possibly used "hindsight". What he did would appear to be brilliant nonetheless.
David
"When you do not know where you are going, any road will take you there".