Thanks for the suggestion! Putting a piece of foam there works *fantastic*! You can't see it when it's on, and it leaves just enough of a gap so the return edge doesn't touch my back.
Thanks mate, so it's really all about not having the gaps vs something fundamentally wrong with it being an extra bit. As long as it visually looks like its a complete continuation of the helmet I'm going in the right direction? Very helpful, thank you
Hows this look:
might make the centre spine a little thinner on the left side to make the left top trap bigger in area. I had used the base print file so theres an extra 3mm width over all that needs to be taken back to accomodate the thickness of the plastic.