Ok, my bad... I shouldn't have tried to post anything in as little as 2 minutes. I think the graphic you guys are looking for is this one.
I will make my argument again, but this time I will try to make more sence (although I am posting quickly)
I will equate #20 to a grill block blocked from behind; Cd 2.30. Is this right? No. #20 is taking into account the separation around the edges which pushes up the Cd, but we will say this is conservative.
I will equate #18 to a grill block blocked from the front; Cd 1.98. Once again it's taking separation effects into account that are not there on a car, but once again, it's conservative.
I will equate #14 (or #13) to Aerohead's redesigned truck nose or the Aerocivic's redesigned car nose, where the shape just gets redefined; Cd 1.16 (or 1.20). This is where you see the big gains.
Between #20 without edge effects and #18 without edge effects, you will be hard pressed to see a difference, since you are talking about a 15% difference on maybe 1 or 2 square feet on the front of a car. Reshaping the nose will make a big difference, but some don't like the idea of losing the auto's original sporty looks.
This is what I was trying to say. I chose a bad analogy, saying that a flat plate like #7 Cd 1.17 would slow you down less than #9 Cd 1.42, but would slow you down all the same. Here the difference is about 20%, and in the overall size of the openings we have on our autos vs. everything else that's going on, it's going to be hard to see the difference.