Finally got around to putting together some side skirts. It used up all of my remaining useable coroplast, but it's done.
I put an extra piece in front of the skirts inside the front wheelwells to help keep the airflow from pushing too hard on the skirts. This also made me notice where the accelerated corner wear on my tires came from- the wheelwell itself. It's barely rubbing against it when I turn.
The skirt is 5" long, and hangs about 3" under the car. I used metal brackets screwed into the body to mount the skirt, and Gorilla tape to secure the coroplast and cover gaps.
We'll see what kind of effect it has as time goes on. I haven't gone driving yet.