Alex, agree with you. Your experience with fin only fences / short fuse fences is a strong point. The extended nose part fences seems to be a problem. What do you think about spiral airflow from the prop? It looks like a cone with highest speed and pressure especially in the nose part. It seems that short version of your fences is a better solution – less influence of spiral airflow.
It would be interesting how your extended fences interact with coaxial propulsion system generating less spiral flow?
Of cause, it’s only assumption.
Sergey