The difference between the harrier and the UCD is the fuse length. I have one called the Phoenix Toptar that is the same. But the majority of these aiirplanes are shorter. So, the UCD 60 is 65" whereas the harrier / Topstar are more like 55". It means the UCD can fly pattern but not these other airplanes; the shorter tail moment makes them more profile-like in behaviour

Ameyam