this one is scaled closely to my head size . my Head is average ... least i think :B
to get the Height on the helmet .
you'l wanna have it from top of your head to just below your chin , which mine came to 26.7cm but added 1cm more to add for space just in case.
Or from top of your head to half way down your neck . whichever works for you.
width: alittle more harder since the horn at the size .
from your middle of your Forehead to your ear 11cm since the horn is near just x1.9 of the length so i gotted 21-22cm
Depth : with thoses 2 measurements added, your depth should be just on the point, Mine came to 27cm * measured side of my head it just had 1 inch gap left for a near snug fit .
I'l need to pep these's 2 pieces to check if they've worked out right or if anyone has done it leave feed back on the result~