I've gotten this much further. But the drawing and that picture don't show the boattail very well.
The boattail is full length to the reverse camber, or could be truncated to a 45° angle at the solid bulkhead or the original vehicle length at the open bulkhead.
The redwood strip version could be made with flexible sheets in simple curves. The sides flat but twisted and the center one bowed with curved edges.
If I built the photoshopped front end instead of a bubble (as suggested by the highlight), there would be three flat pieces like the Shalaho or Grumman post office trucks, but the center piece would be a hexagon with the side triangles following a line that sort of folds over the edge. I should document that. Here is is before being 'hexagonized':
Can you see how the angles on the hexagon would be about where the quarter panel ends? With the bottom edge the width of the spare tire, it could fit on an unchopped front valance.
The current plan is to leave the front as-is with a flat aluminum bar bridging across the two horns that are what's left of the quarterpanels, with headlights hanging from it. It will have a Superbeetle gas tank where the back seat used to be. I'm backing off from the electric motor conversion.
The next round on the boattail will be in a material called Omega-Panel. The pontoon fenders are also further defined but not documented.