Finished "blending" the undertray into the bottom of the tail today.
Then I recorded more tuft tests. Haven't looked at the video for results yet, but based on a couple of stolen glances at the laptop underway, I'm pretty sure it's better.
Got the taut garbage bag skin on, which helps even out and hide the dips & seams. Tuft testing the top & sides is next on the to-do list.
The last test will be an A-B-A comparison at highway speed on my flat, straight test road.
Until then: more pictures!
Below: undertray from 2 angles:
The angle of this pic makes it look like the cardboard is close to the muffler, but there's a 3 cm (~1.5 in) gap at the closest point; most of the cardboard is over 2x that distance away. Also, it's not enclosed as it might appear, it's fully open to the wheel well.
Below: plastic skin & view from above:
