You can make them lower, bro! They probably don't cover enough real estate to do much as-is. Black Widow's are fully horizontal, and they come within a half inch of the rear tires. The trick is to flare them out ever so slightly at the bottom, which is accomplished when you attach the front and rear lowest screws/clips.
I would test them for a full tank, that'll give you a better idea if they are going to be worth permanently installing. If you're questioning your instant read-outs, there's nothing like a full tank's mpgs to average all the conditions out.
I don't have any instrumentation, but in all honesty mine really don't make much of a difference, maybe because my wheel wells are smaller than the average car's. They definitely get people talking about the car, though! My installation is on here somewhere if you want to see how to NOT do it, lol!
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