I just ziptied acrylic disks on all sides of my Mazda CX-5. I cut them out with tin shears so you can see the wheels through them. Just looped them around the spokes and used two holes on the disk. I did the upper grill with a thin clear sheet like Vekke shows in one of his videos. Wife approves
My instant mpg reads 3 mpg improvement when I'm climbing medium hills at around 50mph. I'm averaging 39 plus mpg in mixed suburban city and pulse glide engine on. I'm still learning how to drive this versus the tdi to find the best way to deal with hills.