The airdam is a good move.I would recommend,that if you had more coroplast,that you shingle a bit more behind the trailing edges,wrap it tight against the sides,and bring it as far rearward as you can without scrubbing on the tires.( current NASCAR noses would offer a fine example to follow)
I'm concerned that as she sits,the lower sides are directing air outward instead of back,and this will aggravate the flow along the sides.
My pickup responded very favorably to this kind of setup,I think you'll be well rewarded at the pump.
