Supplies:
Big Head, small helmet, winter glove or kitchen mitt, heat gun.

Procedure: Turn that heat gun on Hi and move over areas you feel pinched by. Within seconds foam inner liner will start to warm and shrink. Be warned, you don't want to make the helmet sloppy loose. With that glove on, you can now start shaping the area with you gloved thumb. Worked great on the Bell Rogue which is made way to narrow for the normal head, or even a mutant biker head like mine.

Let cool, insert head.