Is your helmet slipping back over your head/forehead as you ride? That could be causing it to create more pressure.
I've experienced the pain, though as well, and it is not cool. It usually happens to me when I show western and have to use someone else's hat and its not a perfect fit, and man, within five minutes, I've got an extreme headache. lol.
Your idea sounds good. Some helmets, like mine--an IRH--includes removable and additional padding strips that you can use to help the helmet shape to your head.
Opportunity is missed by most people because it is dressed in overalls and looks like work. ~Thomas Edison