I took a bit longer ride today and can say this:
- Wind coming into helmet from bellow is gone
- Wind hitting my waist and chest is gone
- No buffeting, just like before installing deflectors, as I have Givi Airflow
- Up to 80km/h, helmet is completely silent, then the noise begins. My helmet is noisy, AGV Compact Course, that's why I ride with bluetooth earpieces, they work as earplugs and phone bluetooth in the same time.
So, it was not worthless upgrade. I like my bike better without deflectors but they do help in controlling the wind.