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numbers
Brett,I come up with same modified Cd as Darin ( 0.358 ).
From Kelley & Holcombe at GM in the 1960s,they'd say that the 14.8% drag reduction would net you a 7.4 % mpg increase at 55-mph,and 8.8 % at 70 mph.
These relationships assume a constant BSFC which in the real world does not exist.
The other context,is that when this research was conducted,pickup Cds were in the neighborhood if 0.55.
In 1988 when Texas Tech published their paper,it was right after GM's introduction of their body in white,all-new pickup,which cut the Chevy and GMC drag from Cd 0.535,to 0.45.
In Tech's paper,they mention that the aeroshells benefit can be matched by a re-design of a pickup.
It's probable that modern trucks may not respond to aero mods as was seen with the F-150 tested by Tech.
The only claim they can make, is that an F-150 of that era,would see a 20 % drag reduction with the aeroshell.And this would be under SAE test protocals,with results normalized to standard temp and pressure,something very difficult to carry out.
Your shell mirrors the architecture of the aeroshell so closely,and respects parameters understood very well,for going on a century now,that as far as 'performance' your shell would have to fall at the high end of the curve.It's just that good.
To learn the most from our mods,we would have to do as comprehensive as testing as SAE.Short of that,we're going to see some 'scatter'.
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