Quick tip from someone who's assembled a 3D printed Helegak file...you'll probably have to trim the piece with the 3 cheek tubes to allow for the jaw tube to fit properly. As I was assembling the mask, I left the jaw tubes unattached so that i could get good primer and paint coverage on all the surfaces. But once i started assembly, i found that the cheek piece was in the way where the jaw tube connects to the chin tube. This meant that when i applied acetone to the tube surfaces to bond them together, the cheek piece was putting pressure on the jaw tube and wouldn't allow for a good bond between the ends of the tubes. This also messed up the alignment of where the jaw tube connects behind the ear.
I had to cut a rather large rectangle of material out of the cheek piece to give the jaw tube room to fit properly against the mask. I cut out a little bit at a time until the end of the jaw tube could sit flush against the chin tube. It fits fine now, but it popped off the first day of Dragon Con, so i had to trim out more of the cheek piece that evening so I could fix it for the next day.
Also, and this is up to you, I did not connect the other end of the tubes to the space behind the ear. I found that when i was taking the helmet on and off, the helmet would flex ever so slightly, and that join point between the tube and the ear was being stressed. Eventually that bond broke on both sides. But since the tube is glued securely in place at the jaw, the tube behind the ear just stays in place without glue. Just make sure your alignment is good when you're glueing the jaw tube to the chin tube.
Hope that helps, let me know if you have any more questions. Assembling the mask was a long process, but it was totally worth it.
