Comment by kqr

Paper airplanes do not have barndoor wings, though. Most of them have stepped camber through the way they are folded.

It's not finished but I started writing this to clarify: https://entropicthoughts.com/paper-airplane-aerodynamic-stab...

Scroll down to "trim and angle of attack".

(I hope there's nothing embarrassing in there. It's an old, early draft.)