The reason that the SR-71 surprised me is that it seems like it doesn't have that much wing area (which is probably somewhat counterintuitive given the length), and it wasn't flying at a significant upward angle like those foamies.
Ahhh, if I remember right, the whole thing is basically a wing, and will fly at some slight positive angle of attack.
As far as the model goes, it is probably constructed to be extremely light. It certainly appeared to have quite sprightly performance, implying lightness, since ducted fans aren't known for their especially high thrust.
