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
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.
Be the change you wish to see in the world
what were the mythbuster guys using that was showing the differences?
They said they were using some kind of high-accuracy flow meter (in the 2nd video; in the first they just ran a specific amount of gas until the vehicle stalled from running out of gas), and I am not confident that it was really showing them the difference anyway. I'm pretty sure that the amount of the difference is totally lost in the noise of the uncontrolled variables.
The ScanGauge can't even directly measure fuel flow rate; it calculates a guess based on other variables, which is why it's necessary to adjust it manually.
Anyone tried a partial bed cover? One that covers the tailgate and rear 1/3 to 1/2 of the bed? I seem to recall reading that such a setup reduces drag against the tailgate without breaking up the circulating bubble behind the cab. I imagine the ideal length to leave uncovered would be slightly more than the height of the cab, measured from the floor of the bed.