Using a template bit, I’ve taken the 12mm template to the same internal lines as the 6mm. I’ve left the curved edges offset, to allow for sanding (and to fatten the side walls a bit).
Swapping to a smaller bobbin on the sander, I’ve tidied up the internal curves.
As far as I can take the template at the moment. Now the bridge has arrived, I can properly mark out the locations of the bridge and pickups. I think I might need to shift the pickup positions – hence not cutting them into the 12mm template. Once that is done, that’s about as far as I can go with the template before the neck is further along.