I have done some more serious reading about CYA and its effects and was surprised by the findings.
CYA basically trades chlorine power with chlorine longevity. Trying to better understand the tradeoffs I have been looking for numerical test results.
I have found the following, as can be seen in the attached graphs:
1. 95% of the chlorine longevity benefits is achieved at CYA levels as low as 20 ppm
2. CYA level of 70 ppm is a saturation point for chlorine power, the power stays almost the same regardless of the amount of FC.
If these graphs are correct then I see no reason why to use more then 20 ppm CYA since you can get most of the benefit without scarifying too much power.