I have fucked a bun with that length hair once. It was light brown silky wavy hair and I'll see if I can find a picture of a bun like it. It wasn't a sock bun but more of a loop bun with a bunch of intertwining parts. I loosened it a bit to push my cock in all the way through the bun. The bun was about the size of an orange. And it was heavenly!!

So I know I would love to fuck one of those massive Indian Rapunzel buns!

Sort of like this blond bun:http://lasthairmodels.com/2012/08/31/tall-buns/tie-hair-bun/