on mine I have to be honest I just scratch built it from cardboard adn tons of bondo. I actually didn't bother with the neck guard from the pep. Originally I thought it needed to be a separate piece, and that how it was going to be in the movie but now with more images available it turns out I was wrong. I'd say just hot glue it as best you can.
The scale should be the same but if you need to change the scale let me know so that I can resize it.