I have already done some tests on small Depron planes with Airmode and low rpm running Betaflight. Basically it works as long as a thrust vector can be generated (the hover engines are far enough away from the centre of gravity). A control effect only from the torque unfortunately did not work and requires an additional inclination of the drives to achieve a sufficient control force e.g. for yaw. Or 2 propellers with differential thrust are used for the wing flight drive. I´ll try to implement a small vtol variant without servos in the near future with PX4 on small targets like Omnibus F4 Nano with 2S or PixRacer 3S. Even with the BLADE Inductrix Switch AIR not all but only the rear 2 drives are swivelled to get more yaw authority. A Quad Tailsitter without servos has a missing aileron effectiveness and doesn’t look nice either, because the drives have to be far enough away from the centre of gravity.