First dimensionally accurate model a 16 led Neopixel ring from adafruit
Then define a body space gap with the model so you can use it as a boolean operator against the piece you wish to mount it in.
Design a test piece to test the body space fit.
Print it, low material use compared to final part, so you can afford to iterate...Be amazed when it fits like a glove the first time.
Model it directly into the target part...
Prototype your electronics.
No easier to video when in the helmet, trust me, it looks fab...
to be continued.