Charles, you mentioned plans? I’m sure who ever left them for us to discover had enough foresight to realize how primitive the roots of our measurement system really was? It is really funny actually once you become aware and hence my lifelong skepticism of the accuracy of the pyramids. Take a look at the history... Medieval barley grains...
http://www.dozenalsociety.org.uk/history/feet.html
You keep mentioning 10.5’ but was there a scale with that? They can’t be too old because our system is relatively young itself so was the 10.5’ number a “translated” measurement?