While in engineering (critique) mode
Mart,
Here is an engineering challenge for you.
The earlier S-69 used a pair of jet engines to provide forward thrust. On the X2 the single propeller must produce the large thrust during high speed and high drag flight.
This thrust will be accompanied by a large torque, which must be counteracted by the fuselage. Airplanes have a large wing area to handle this torque, however the X2 has a very small blade area. What effect will this laterally unsymmetrical loading have on the craft?
From pictures it appears that Kamov's solution is coaxial propellers.
Dave