Kammback
Backyard:
If your trunk lid is still available, you should build off of it. You can this way use the seals and steel to get you started, and build up from there. This way you may even be able to open and close your new kammback hatch! If you use some Lexan for windows (for visibility) you would really have something. I have seen where cars with your design (fastback hatch) have had the hatch replaced with a "station wagon hatch", giving more interior volume. I don't see why you couldn't do the same while making your vehicle more efficient.
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