Actually, I don't know how I could achieve 35mpg in the Insight. Closest I ever came was 41mph, driving fast, into a storm.
My first car was a 1996 Subaru Legacy, 2.2L, 5MT. I loved that car, but the fuel consumption was out of line. By driving carefully and using a kill switch, a grille block, and a ScanGauge, I was able to get 31mpg, versus 27mpg the previous summer.
Next time you need tires, you should look at narrower ones. The Outback may have come with 225's, but the Legacy did fine with 185's. There are also LRR tires available, maybe in a silly SUV size like the Outback's.
Block off the upper grille first (someone here did a neat job in spandex), because it has a bigger impact on aero. Then block as much of the lower grille as you can.
Too bad about your transmission always downshifting. Good luck with your car. 35mpg is a bit ambitious for a 22mpg vehicle, but some folks here have achieved even larger % over EPA.
Edit: Now I see your pics! Hmm, with that foil in place it reminds me of the work of
Istas. The nice thing about fiberglass is you can paint it body colored and make it look as good as OE if you're willing to spend the time on it.