To really solve this, it seems like the whole perspective projection code in Camera3D might need revisiting. I'm not sure that formula accomplishes what you want it to, in terms of distortion (fisheye) to telephoto (flat)
The problem seems to revolve around the perspectiveProjection class being inherrently controlled by stage.stageHeight and stage.stageWidth - http://livedocs.adobe.com/flex/3/langref/flash/geom/PerspectiveProjection.html One way around that is to set your focal length to a high number like 10,000 and your z translation (_focus in the code) to a high number like 400 and get rid of fieldOfView assignment. This will create a very undistorted projection - i.e. no fisheye. The fisheye seems to be rather innaccurate anyway.
