Once the indicator gets close to 45 degrees it starts to 'spill' so much wind that it starts to lose any meaningful indication. I next divided the rest of the arc into three equal parts. This also turned out to be a great discovery. It was simple and easy to read at a glance. On some of my bigger radius indicators I have gone to 4 equal parts but I learned that the larger size did not justify the logistics of transporting and the set up of the larger indicators.
To keep it simple think 12 to 13 inch radius and minimum markings. Less than 12 is to small and larger than 13" brings diminishing returns.
As for the Indicator paddle I tried every shape I could come up with. The airfoil shaped Styrofoam in the top example was the best and just a flat paddle was next. I found that round shapes like balls and using plastic cups were not as accurate. If you notice this general philosophy is carried through all the flags I make.
The secrete to reading the wind is to build your own indicators and experiment with size, shapes, and markings off the range. That is the only way to make the wind your friend!!
That's my Story and I am Sticking To It.