The following drawing illustrates an extension from the subterranean passage as measured by Petrie from it's entrance.
Petrie's calculations indicate the total length of the passage equals the distance to the top corner of the "Great Step".
Again I ask for any who can confirm these measures since they are required for further proof of development for the pyramid's main structure.
Without question, Khufu's pyramid with it's three chambers was a single design...set before ground preparation commenced.


Best.
Clive