Julian E. -- I believe you. But then I simutaneously believe in 'gut feelings' and 'confirmation bias'.
Are you familiar with the work of
Yoshi Suzuka? He's been at it since the mid-70s, like you and aerohead, and talks at one point about up to 1500 component tests a month, using miniatures for preliminary work before moving to the full scale tunnel for fine tuning, and how power required grows with the cube of the volume of air (or something).
Late one night, in a certain frame of mind, I got to thinking about wind tunnels with multiple propellers needing diffusers to smooth out the resulting flow and I wondered—why not paddle wheels? I did this and posted in another thread:
More lately, I'm thinking only two wheels, at the 'stern' and shorter, thin walls with fillets that concave up against the sweep of the paddle wheels.
Less turbulence? On-topic for air tabs?