There is a huge difference between the angle of sweep and the inertia and mass between an F3A model and an airliner size airframe - the type of aircraft most likely to suffer from Dutch Roll. I have not noticed this at all with the Anthem - the wing sweep is quite modest so even in full size I wouldn't expect Dutch roll to be a problem. The other problem with yaw/roll coupling is that most full size aircraft, apart from aerobatic machines, tend to have the entire fin/rudder above the centre line of the aircraft. Application of rudder will then always induce roll especially as most full size have dihedral. Our F3A designs have half the rudder area above and half below the fuselage centre line so yaw does not produce roll. With a swept wing any yaw induced by rudder is counteracted by the swept wing - at least that's the theory. For the Element, moving the CG aft eventually cured the roll/yaw /pitch issue. For the Anthem, I still have a small knife edge mix to prevent roll and pitch when flying KE. I have moved the CG to the neutral point but didn't like the way the aircraft felt so I have a slight push force needed when inverted.

I have to say that I rather like the sound of a contra and, certainly, with the Debowski TMCR, the power. I have recorded a maximum of 3,600 watts with the TMCR in a vertical climb starting at a very slow speed. The Hacker Q80 in my Citrin could only manage 2,850 watts in the same situation which is fine as the motor is rated at 2,800 watts. The other problem is that it is so quiet I cannot hear it in the air - probably means my high end hearing is shot as well! The contra at least gives some sound to throttle movement. I may well revert back to a single prop solution in due course as I think there is little that a contra has over a single prop.