Cores/molds make a lot of sense. I worry about stiffness and fragility of the typical 3d printed ABS/PLA being used directly as a foil. But most of my experience with 3d printers was years ago and maybe there are better materials since then?
Even high end 3D printing materials are no where near the strength of the most basic Carbon Composite wings currently in production. #D printed molds & cores could(& have been) used to good effect.
