@mildred's people and Vincent: YA does not allow me to edit nor allocate BA. Will try later with other browser.

Your advices are noted: reducing the hub dia, increase the blade length.

Thrust vectoring: Correct: I have a problem with that. Making a vertical fin (changes the shape a bit...)

Still working on the swach plate: bearings hard to find!

Any other advices?

Should I create a small forum for interested people to hlep (aeronautic engineers, pilots) ?