To start off, this is my son's last Halloween and he wanted me to make an awesome costume.  We decided on Halo armor.  After a little research, I decided on foam armor but a pep helmet.  So after many nights of coming home from work and cutting pieces then finally gluing, I was a little unsure of the size.  It fits over his head but afraid that it may be uncomfortable.  Attached is a photo but I'm trying to figure out the best way to possibly cut it to widen the sides a little.  Has anyone attempted this or have advice as to where I should try to expand?