Finally got a dry day to redesign the kamm. I flattened out the sides and trimmed 2 inches off of the overhang, but I needed to clip some off of the side to allow the trunk to open.
I also redid the supports and got them more evenly spaced, and gave it a nice gradual curve over the rear glass.
EDIT: Either today was a good day, or the change really helped. My usual coastdown check went farther than it ever has today. There was a bit of a breeze out (crosswind), and the temp was around 60. I finally hit 35 MPH at the second 35 speed limit sign, when I usually come to that speed at the city limit sign between the two 35 limit signs.
EDIT 2: Another coastdown test today was close to the last one. A semi truck slowed down my coast a bit, though.