I broke my rule and tried multiple things together. Servo change along with aerodynamic changes. As a result, it took me a while to pinpoint the problems. Finally, figured it out and had a good flight.
The fact is that the elevator/rudder combination on the legs didn’t sit well. Because of the nozzle design, they got into the airflow and disturbed smooth operation or the nozzles. Also, the servos turned out to be more responsive than the old ones, which caused me having to operate with the lowest P value in the history of Monos.
Now, since I need the elevators and the rudders in horizontal flight, I will need to come up with a solution which will not disturb vertical flight.
Below is the first long flight. Considering that there have been some major aerodynamic additions, it is very good. I felt very comfortable and did a couple of small loops around the park.
https://www.youtube.com/watch?v=YuzY4C_8qrM
https://www.youtube.com/watch?v=YuzY4C_8qrM