Can anyone tell me how much headroom the upper deck seats on the 747-400s have? I am pretty short - about 150cm/ just under 5 foot - and I’m wondering if I would be able to stand up straight in my aisle seat (not exit row). I watched some YouTube videos and certainly some people in them were too tall to stand in front of their seat, but given I’m pretty short I‘m not sure if I’d be ok. I’d like to be able to stand for some periods as I have some back issues that get worse if I sit for too long.