The whole trick is to stop your head moving in relation to anything. If it hits anything your dead or your neck will be broken.
Which is the reason why you meant to curl up and put your arms over the top of your head. Up right with your arms in front of you will just give your head 50cm to gain a relative difference in velocity between head and object your going to strike. Plus also your neck will flex and give whip lash damage.
So pull your seat belt tight and kiss your knees and pull your head down and keep your elbows tight in.