I will see about the cloroplast after Nov 2
otherwise I was going to try foam like 3wheeler did.
I have a call into a junk yard to see how much a spare hatch would cost, if it is reasonable I will pick it up and have fun
That one I will weld up a frame for the shape of the tail, then cover with what ever material I want.
You are right about making the back as small as possible. I wish I could draw it up but I am having issues importing a pic to base the design off of. Oh well.
I think for length I can get away with 6" on the top (the Kammback is 22" and is even with the back bumper).
What evidence of 20-30% gains do you have? that seems high to me, I was guessing about 10-15%.