Stay in the middle of the air. Avoid the edges.
I was on holiday in one of those zillion floor hotels a couple of years ago, I was on the 23rd floor and I think it had around 40. It had a large balcony with a decent sized barrier. I'm fine looking out horizontally or downwards as long as it's not vertically down. Vertically down isn't pleasant, but the thing that really made me tilt was sticking my head over the balcony and looking
upwards towards the top of the hotel. (If you're wondering why, I was trying to create an interesting camera shot...
)That was serious weirdness time; luckily I had the sense to fall to my knees otherwise I think I may have been over the barrier.
Put me in an aircraft and spin me, loop me, no problem, love it. I can look straight down or up out of an open cockpit no problem. I think the major difference is in an aircraft you're sat down.