I'm 183cm and there's easily another 15cm above my head, if not more.
Well, I have to slouch a bit to be OK (head clearance) with pretty much same height or 1cm less and Bose X headset in R22. I've seen taller guys flying R22, although their knees and torso remind me of harmonica.
It very much depends on the ratio of leg and torso lengths of an individual.