[brucepick]

Thanks, all.

Well - - -
It's not a Kamm back, at least not now. You could call it a spoiler, or a false, lifted trunk lid, or maybe a short Bonneville spoiler. The reason for the design is I want to be able to open the trunk and see out the back. If this basic design would give aero improvement, I have a scheme to make 2 cuts across the flat panel, that will allow the trunk lid to open. I'll spare you the details.

I'll try lowering the horizontal panel's trailing edge. I can try a flat panel over the whole assembly, making a Kamm that goes to where the horizontal panel currently ends - though I think that will kill the scheme to open the trunk. I would trim down the rear of the fins for that. But I will want to test that concept before I start cutting the fins away completely; the forward part of the fins are part of that Kamm design.

I can also reduce and then eliminate the fins. That would make it pretty much as if it were made with a taller trunk, with the trunk trailing edge at the template point.

Oh yes - I have another idea, completely different. A span of clear flexible plastic, the heavy duty stuff for temporary storm windows, stretched across the whole area from roof rear to the current spoiler rear edge. Maybe some bow strips going across to keep it from sagging in the wrong places. Detachable at the sides (velcro??) so you can lift the trunk. But as I said, that's a completely different concept.