I made a pepakura iron man helmet but the one problem is that the opening is too small for my head but when I force it on it fits. Does anyone know a way to make the opening bigger or have something open up so that I can fit my head in. A while back I found a video of someone pushing up the back of the helmet but I can't find it or anything like it. Does anyone have any tips on how to make it easier to put on my head?