My DH is 6'4" and we have never experienced any problems on any of the rides, certainly never been kicked off!!!, although some times things do seem to whizz past your head a wee bit close (I'm 6' so also experience this a little) - why are us tallies always penalised!
Any way one good thing I can't wait for my trip in August as I always buy loads of clothes especially trousers to fit me as they are had to come by for tall women in the UK - oh and shoes - its an absolute pleasure in US to buy these......