your thinking of a boat tail.... my car must be rubbing off on you
just think of all the extra space you would have.
if you put a big logo on the tail then its a "work loner car" most of the body shops around here have loner cars that are covered in decals. yours would you be a show off of what you can do to cars.
to make a camera rig, get a big magnet (from an old CB radio antenna) and bolt it to a 1x2 and the it can stick back far enough to work.
you will want to see the sides, top and bottom as the approach the the back end.
for the belly pan, after looking at all the pics and diagrams I think you want it to taper up to match the bottom of the back bumper.
go ahead and make your pan, or wheel well covers out of paper mache, then once that is dry it will make a nice mold for fiberglass. I can walk you though how to do fiberglass. you should have no issues. I did my whole tail and had up to that point only ever used fiberglass to patch a small hole in a canoe.