Marc, we have never met, looking forward to someday. The original vertical area concerned me from the onset and flight showed my belief they were inadequate. They were increased significantly in two steps and showed little improvement in stability. I was never a fan of BLENDED WINGLETS( there, I said it too) and suspected significant wrap around flow vertically up the winglet at high AOA , thereby compromising the flow over the winglet. That is when I figured a fence at the inboard point where the radius began should likely help . It arrested the dutch roll tendency, locking in the airplane when rolling into and out of banking. It also, not surprisingly, require adding significant amount of up elevator trim after their addition telling me the wing was now also producing more lift, again no surprise to me, and working harder. I then suggested we do stall testing and he scoffed at that and said everything is fine now , time to build the real one. So all bets are off as to how real articles stall behavior plays out. As I said , I have suggested many required test considerations, only to have them scoffed at. Don't like to throw hands up in the air but what else could/can I do. He thinks he knows it all.