RE: zAGI 5C
When you fly back into the slope, and you're flying slow. It's most likely you're going the same speed as the wind. Or not fast enough for the air to pass over the elevons. So your wing isn't going to do anything but hit the hill. That is why you NEVER fly downwind on a slope unless you have enough speed. Always fly parallel to the hill and keep the nose pointing the wind.
That's my opinion..
-Tomi