one thing about being on the gas really deep is to remember that at some point you go into open loop and your a/f ratio changes because it puts in more gas to give you more power. some vehicles (like theholycow's VW) has a wide band 02 sensor so it doesn't do that.
another thing about the slope of your truck bed thing. I have heard 11 degrees and 10 degrees but any mor than that and it might as well be straight down because the air is separating and causing drag. if you want a good example of the ideal slope, look at the back of a toyota prius or for a home made version here is basjoos' car
http://www.gassavers.org/garage_imag...12g66c7b6f.jpg
his car is "keeps on rollin" and is in the top 10 for gas vehicles (but not in the overall top 10 because of the motorcycles) he just replaced the motor and is now getting 78ish MPG. now that is impressive.