67mpg? That is insane!
Have you tried making the airdam lower only on the sides, in front of the tires? I believe this is the new trend in OEM airdams. The lack of the middle part reduces frontal area, but the extra air going under the car doesn't increase drag too much because of the smooth bellypan.
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e·co·mod·ding: the art of turning vehicles into what they should be
What matters is
where you're going, not
how fast.
"... we humans tend to screw up everything that's good enough as it is...or everything that we're attracted to, we love to go and defile it." - Chris Cornell
[Old] Piwoslaw's Peugeot 307sw modding thread