Searching in the dim, dark recesses of my mind Alexis, I think Eduard are correct. The tailplane was like that - there was a story that the Pfalz was a real favourite of balloon - busters, and the usual tactic was a screaming dive from altitude to avoid the flak, and the Pflaz was a good "diver", and then the inverted tailplane aerofoil helped pull it out of the dive at low level... Now I can simply not remember where I read all this, let me peruse the books! Regards, Marc.