RC KFC bucket aeroplane (magnus effect)

I've only seen Peter in his guest spots on Flite Test. One of the sweetest and coolest dudes on that channel. Always down to experiment and obviously thinks big. Edit: Case in point, magnus effect plane - [VIDEO]

Potential flow theory tells us that the lift L is L = rho U Gamma, where rho is the air density, U the flight velocity, and Gamma the circulation, i.e. the tangential velocity of the rotating surface times the circumference. L is then only proportional to the radius, not to the square of the radius. But it sure does produce enough lift to let things fly! [VIDEO]

My understanding is that planes don't fly directly upside down, and they angle the wing slightly to make a kinda-sorta-airfoil. How helicopters can turn directly upside down, and fly that way[1], without reversing the direction of their props, that I don't get. (Thinking about it now, I think it turns from a helicopter to a hovercraft? Eg, this is a ground effect?) [1] [LINK] Also, tangentially, Magnus effect planes are a thing: [VIDEO]