BTW, that upside down wing trainer has a really bad yaw in roll. It's got a wing that's nowhere close to symmetrical airfoil. And the anhedral seems to want to work in roll opposite what a dihedral wants to do. So I've changed the single aileron servo to give differential aileron. Been wanting to ask an experienced anhedral flyer about that........ so...........

Ed??? any observations about what anhedral acts like in roll? and in yaw?

I've noticed that on takeoff (low airspeed) when I aileron roll and pull some elevator the nose yaws out like crazy. I've yet to fly the differential setup, btw. And when I yaw the model on purpose, like for crosswind landings, it just yaws; I don't see much roll (either direction, clockwise or counter). Is that what they do? Or is the cambered airfoil mixing up things?