Body plug ended up being 8 pieces rather than 4 because of the curves and tooling, a big thanks to Steve and Joel from the CNC place and to Woody for making it a reality.
Cut the tail extension from 6mm (1/4") marine 5ply, routered a 3mm (1/8") recess in both sides of the mating surfaces of the rear quarters:
The tail piece goes into the body 500mm (~20") to make sure it's true with the centreline:
Got it glued up;
Bit of light sanding and spot filling tomorrow then first coat of glass hopefully.
Best thing I've bought lately, a set of 5:1 epoxy pumps, same number of pumps from each and the ratio is right, no more measuring cups:
Cheers
jon