Try this menu of choices. You may have to click on a few to get your answers but what you are looking for is probably there. If not send a e-mail Warren Beauchamp the guy who runs the web site knows a lot about HPV's and fairings. He'd be glad to help you. I speak form personal experience when I built my tail box.
Here is the link:
http://www.wisil.recumbents.com/wisil/whatsup.htm
Good luck.