[QUOTE=BeeHoney;8177056]
People with regular hair don’t understand what it means to have thick hair. There is no way I could grow my hair halfway down my back and get it up in a helmet–any helmet and any size–without completely compromising fit and safety. I’m guessing you are in the same boat. I’m sorry to be the bearer of bad news, but I’ve been there. [/QUOTE]
I have very thick hair and have had it VERY long at times. At the moment I don’t like it very long as hair that long kind of grosses me out. Not sure what changed.
I do currently get it thinned (because I’d like to be able to put it in a ponytail or some such and without thinning I can’t find bands that will go around it more than once.
I can fit it in helmets and they fit within the same standards used to determine if a helmet fits any other person.
this rider has long hair and doesn’t wear it up. It’s actually in a braid down the inside back of her coat. I was worried that it would show, but you wouldn’t know it was there if you didn’t know her.
The good news is that 1) riding/showing is way more fun than having great hair, 2) you can lop your tresses off and donate to Locks of Love and feel great about that, and 3) shorter hair is more in fashion now anyway. 
I don’t recommend Locks of Love if you are going to donate. Do some googling. Their practices are questionable at best. I donated to them twice and regret it.
http://www.forbes.com/sites/quora/2013/05/13/locks-of-love-6-million-of-hair-donations-unaccounted-for-each-year/