Really excellent model - thank you to the designer for this!!!
I used Hobart welding helmet head gear but wish I would have used simple hard-hat head gear because the low strap on the back makes the helmet difficult to put on. I added voice-activated LEDs in the mouth so that's why the wires inside. I found it very easy to add and route wires. I'm driving the LED circuit with a single 18650 battery which fits nicely into the top.
I used a solder iron with old tip at 250F to join all of the pieces. I haven't done final filling on the seams on the outside. I filled the seams on the inside because I wanted it to be solid and strong. On the outside I'll probably do a little plastic fill and a little bondo.