Since we are talking Indiana Jones and jimbo's almost apparent lack of BTS knowledge...
You do know how he kept the fedora on, right?
You do know Ford used a staple-gun on his head to secure that hat. If you don't believe me, I can get screen-grabs from the DVD set. They used footage of it in the menu system.
Also...
*slaps jimbo with a medium-sized fish, as mentioned earlier.