Grimmers How do you get your pep so clean?
Besides just working slow and keeping a sharp blade, a big tip is to score all of your fold lines. Do this by doing a light pass over all the fold lines with your blade, but not strong enough to cut all the way through, just to lightly score it. Take note in the pep file which fold lines fold inwards and outward though, so you don't score on the wrong side. This is with thick card stock paper of course.
Doing this allows for very nice and crisp folds and a very exact fitting.
You can see an example of some scoring I did in this shot I took while assembling:
I also work in big separate sections at a time, then assemble them all together at the end. Easier to manage.
But yeah, a good clean well-assembled Pep will remove so many shaping headaches you'll run into down the line, so take your time. I binge watched like an entire season of The Clone Wars while working on mine.
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As for those asking about sizing. A 100% print on the proper paper seems to be pretty 1:1 accurate to me, I'm not an exact expert on Stormtrooper dimensions, but the few size reference I've had to use during my build seem to match up. Others have already chimed in that it's 1:1 accurate, so I'm pretty inclined to trust them.
As for fit, I have a pretty large head and it seems to fit pretty well. I have to turn twist it to get it on (which I hear is a classic anecdote of ST helms), but once inside it's roomy enough to imagine fitting some internal padding and electronics inside. My beard sticks out the bottom a little, but it does that for everything.
Keep in mind also that many of the most popular helmet sculpts vary pretty greatly in their size and they're all considered 501st acceptable, so you have a pretty good wiggle room to fit the helmet to yourself.