I did a quick mockup this morning with cardboard. The cardboard is held to the clips using M5 screws and I designed a spot on the back of the clips for a nut. It seems that the lip I was counting on for the clips to hold to isn't uniform in size (I measured and test fit using the other wheel well). I'll probably use hot glue to make sure they're secure for testing and use some epoxy or silicone if it's to become a permanent feature. I plan on having metal brackets towards the bottom for extra security. The skirt will have to be shorter to not rub on the tire, unless I want to have it bow out.
I kind of want to go full basjoos (probably a shorter tail) on it and see if I can get it to match the Prius' mileage.
MetroMPG- It took me a bit to find the fuel economy displays in the center screen. I was excited to find that I wouldn't have to make due with the little screen in the cluster. I hope my wheel skirts work out better than the ones you tried on your sister's Camry.