[brucepick]

Yes, the side panels are closer together at the rear than they are up by the glass. I think that's what you're suggesting. Another way of saying it is, the spoiler panel is tapered - it's about 5" narrower at the back than it is up front where it meets the glass.

5" narrower doesn't sound like much, but that's with the spoiler angled slightly up at the front. If it were dead level, the measured taper would be more. Because I'm measuring the front width higher up, where the spoiler meets the side panels.

I got the rear narrowing rate, and also the side slope of the side panels, by matching and following the contour of the body. I'm just trusting that the engineers did a pretty good job. So far it looks like that's the case - my first attempt likely increased the drag.