I started on the actual boat tail today. I decided to go with steel tubing because I have a lot of it laying around and it worked well for the airdam and side skirt rails.
I only got as far as the top surface, for lack of a cutting wheel for my grinder (where did I put them?!), but this is what I have:
It may not appear to have a very nice "parabolic" curve to it now, but it will as I get the actual frame put together. I will use 2 runs of angle iron running along the bed walls to clamp it down with the clamps for the camper shell.