Hi Les,
You're on the right track with Bulkhead and structural supports for the body. Similar to the vintage Rometsch cars there are longitudal structural supports with outriggers off of them supporting the body. There will be a bulkhead support forward of the dash and a firewall just behind the drivers seat. The rear end will open similar to the 550 Spyder and will be completely removable as well. All templates are based off of the Buck. The Buck guides all the panels and structural supports. Of course all of this is in my head, no blueprints here.
As of now the front fender/nose clip is going to be removable but I really don't like the seams on top of my fenders... I am thinking to make a removable front trunk/smugglers hole to access the pedal cluster and steering box area.
Here's a recent picture after welding several of the nose seams. It's slowly becoming one piece.
Chris