Originally Posted by cbr4119

Have I seen a significant accident where someone smack their head on a rollcage/bar? No, I have however smacked my own head on my rollbar (in a Miata) accidentally numerous times and given the pain involved in that my best case scenario if I'm ever rear-ended is a cracked skull.

On a more technical note the danger zone is about 2" past the farthest movement of your head (since your neck and harness will stretch a bit, no not 2" but that's a nice safe margin), if that area is clear you're generally safe. On the hand if you lean your head to the side and it smacks a tube you're rolling the dice and probably want to stick some padding on that tube.

If you're going to wear a 4+ point harness all the time you're going to have much less motion in an impact, 3 pt belts don't do as well.

In the interest of full disclosure I have a tube EXACTLY like I'm warning against in my Miata that I can't convince myself to cover (it was expensive and shiny and I don't want to cover it with ugly padding). It's been like that for ~8 years now with no issues but I know I'm going to be hurting if I ever get rear-ended.