The more similar you can make your device to the bird in question, the more they're going to accept it. We based it on a model glider, but we were still left with this tail that sticks up. We had to work out ways to get rid of that and replace it with a bird's tail. It's a very different craft to fly than a normal glider, but, they accepted like it was one of them. The biggest problem was landing. We didn't have the feet of a vulture. We could launch it off a cliff, but often there wasn't a runway for it to land. It's a worry sending it off a cliff not knowing how you're going to get it back.