I attached the smaller chin part to the helmet with 3 mm screw after drilling two 3 mm holes on left and right side. And I made few shots to compare the size between my motorcycle helmet and mine. Look at the huge size difference. My head size is extra small but full-face motorcycle helmet in my honest opinion has engineering stupidity that has been safety standard over six decades, which is the bigger and thicker make safer helmet.
Most animals have impact absorption layers – leather, skin and muscle – over bones. My approach of safety helmet is that the hard shell should be small and inside not outside that hits impact directly. Helmet manufacturers recommend replacement of helmet whenever it gets serious impact claiming helmet is one-time protection gear at the time of impact. What a waste of resources and behavior of stupid collective.
I think I definitely need to make another mold that has perfect symmetry and smooth surface for the final hard shell.