You beat me to it on the air dam drag- Pinto story. Wouldn't work for me unless it had a Batmobile drop/retract capability for offroad use. I do think fiberglass is the only practical material for that amount of surface area. Even then it would need some bracing at the bottom edges. Profile drag is the greatest issue affecting truck mpg, and the one we can realistically change the least.
My experiments agree on the accelleration theory...slower accelleratin to cruise speed is less efficient than moderate. I have found 55-65 mph to be the most fuel efficient speed for my truck; 2006 4x4, S-CAB, 6 1/2' bed, 4.6L, and stock size 17" tires. At that speed I get about 18-19 mpg on county and state roads with occasional town traffic (a 50/50 mix of rolling hills and flat ground). My only mods are the Gryphon w/base 87 tow setting and the gotts mod. Also, I admit I buy the cheapest gas all the time. I still haven't made an "interstate trip" since installing the Gryphon.
For some reason the Gryphon consistantly indicates 2 mpg better than my pencil and paper calculations. I actually got a momentary Ave Mpg reading of 22.1 once. I'm likely going to install an e-fan in the near future, then get a custom tune.
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