That suggestion seems the easiest for me to comprehend. Can anyone verify if it's correct? It seems elegantly simple.
It does look to be correct. But you would have to analyze different configurations and compile relationships for each config. Usually when something is depicted to be very simple, there has been a lot of simplification (that would seem obvious) - meaning that it no longer applies to the full extent of applications. I would be careful to assume that this relationship applies - as indicated - at all altitudes, at all speeds, at all pitch rates, at all Reynolds numbers, at all Mach numbers, etc. There are a huge number of effects that will change this graph. However, knowing that this is a big generalization, I don't think there is anything wrong with it.