Thanks Scott, I kinda like the posts too.  The originals had three "rivets/bolts" that "attached" the post to the back of the seat; I'll see about replicating those (not that they'll be seen, but...).  
This picture shows how the (unpainted) panels and "new" wheel wells butt up to the body's walls:

There are a couple of areas that will get some putty to blend the pieces as you can see...also in each wheel well theres a spot where the glue sort of "melted" the thin sheet; that will also get the putty treatment.  
I didn't take the rear panel pieces all the way to the back of the body because there's a really nice curved panel that will cover everything from the bumper area to just about where the wheel well starts (there's another for the front too).
I think I will still use (five pieces per side) either copper or lead sheet to create the supports that go from the body's sides to the bottom of the tub (body support brackets/stiffeners?)...one at the rear of the front wheel well, one on each side of the rear wheel well, and two in between the wheel wells where the new plastic is.
As I take a relook at the picture, with the new plastic there in the middle, it's kind of "bare."  Even with the stiffeners in, I may need to look at adding something....something that will be a different color than the black.  Not sure what mind you...but something.
Mike