Zee Man;

I couldn't help but comment, I am very willing to put in one cent worth, but this one cent answer not answer your question.
The truth, and nobody else will tell you, is that there is no perfect answer.

Allot of the E-props flex, that is not good. However, on the other side, they are usually lighter, so they allows more RPMs and more efficient motor operation. This is due to less mass and weight resistance. In my thinking, RPMs are a function of Volts to the electric motor, and amps sustain that voltage, however, it stands to reason that, if the prop is thinner and lighter the motor will not work as hard. I think it make the motor operate more efficiently sby producing the same RPMs and use less amps, thus, less stress on the batteries. However the plane won't fly as well as it would, if it had a larger mass non-flexible prop. As you can imagine, there is alot to consider when selecting motors, controllers, batteries and props.

If you want to take time off of work, or, use up your spare retirement time, you can read every build thread on this site and get info on props. In order to save you the time and effort, the answer that you will come up with, is that there is no perfect answer. Every builder experiments and comes up with his or her own performance conclusion. In other words, the method of finding the right prop is to use suggested variations posted by other people or motor manufacturers, then spend more money and try different props until you find some that work best for your particular type of flying.

So, Zee Man, welcome to the RC research and development department. Also you might embrace my philosophy, "just do it"

Al G.