Last summer, I found this Engineering thesis on line which was done by Nathan Williams in September of 2003. He is an officer in the Navy and wrote this thesis for his Masters degree in Mechanical Engineering. He utilized extensive CFD simulations of aerodynamic fluid dynamics and ends up with a fastback style truck cap. He also shows the benefit of a large front spoiler.
It is lengthy but a good read. I wish I would have ran across it before I finished the design of the aero cap I have made.
Here is the link:
http://stinet.dtic.mil/oai/oai?&verb...fier=ADA418232
Click on the Handle and it will download in Adobe format for reading or printing.
In the thesis, Capt. Williams builds a prototype and road tests it. His numbers prove out the design he arrived at with the CFD simulations. Hope you find it as informative as I did.
Brett