The large amount of incidence on the GP GB wing has some negative affects on the high speed flight characteristics that I'm not too fond of, but this larger than average incidence has some benefits for low speed flight because it effectively amounts to additional down thrust. Down thrust helps prevent left yaw causing, asymmetrical thrust at high AoA that that is the result of the right side of the prop arc producing more thrust than the left. As speed decreases, AoA must increase to maintain altitude. Decreased speed also means that control surfaces are less effective, but since the AoA is increased to hold altitude, asymmetrical prop thrust increases. So, we have a situation where control surfaces are becoming less effective and left yaw thrust is increasing. If the aircraft is able to achieve a slow enough speed and high enough AoA that the asymmetrical thrust overpowers the control surfaces, there may be a sudden left yaw that decreases the speed of the left wing (decreasing its lift) and increases the speed of the right wing (increasing its lift). The result can be a wing drop or even a violent snap roll. This is why I think that adding washout didn't prevent the left wing dropping that I experienced. It wasn't the left wingtip stalling that caused the wing drop, but rather the whole left wing losing lift at the same time the right wing gained lift at the point when asymmetrical thrust overpowered control surface authority. Come to think of it, the washout that I added may have made this situation worse because the washout reduced the average incidence of the wing, thereby reducing effective down thrust and causing a need for increased overall AoA to maintain altitude at slow speed. Increased AoA produces more asymmetrical thrust. The fat GB fuse may have contibuted to this loss of lift of the left wing by blanking out some lift on the left wing in the left yaw situation and also by blanking out some (already compromised because of slow air speed) control authority of the left h. stab. Given all this, I'd have to say that the only way to stop the GP GB from dropping a wing is to keep the speed up. I think maybe that the GB's that you've seen that didn't have wing dropping problems probably had owners who followed their instructions properly.

As to the method that I used to add washout to the wing. I just thought I'd give heating and twisting the stock wing a try before doing something more complex and its held for a couple of years so far. I didn't just reshrink the covering to try to hold the washout in place. I turned the iron on high and appied a lot of heat through the covering to the balsa D-tube construction of the L.E.. I also measured the washout with an incidence meter to keep things accurate and symmetrical.