What I hate is hitting the closed hatch while wearing a ball cap, that little button on the top can really hurt and draw blood. Of course, the peak prevents you from noticing the hatch is closed.
I *hate* that. Although, we don't have a hatch on which to leave open/closed, I have hit my head many times because of ball caps in the same way. One way to avoid it is to give up the ball cap in favour of a dorky Tilley hat. Outside of the better sun protection, they also have a foam top which cushions the blow on those hatch/head meetings!