umm.... i think it was snowcase who built a whale tail rail so message him, i think he did it with some box material though, although bending the pvc pipe would be easy enough. Im also thinking about building one. My idea would be to cut the supports with the correct angle that you want and then finish up the frame. Then nail/screw plywood onto that and place the pvc pipe on top of that and screw into it from the bottom or something, im not really sure on how to attach the pvc pipe...