I have sat in the middle and on the ends, I have been on bottom and middle floors.
I get nauseous, dizzy and have vertigo ongoing.
I had NO problems on FoP.
First ride I spent most the ride (long story) looking everywhere, behind, across, above, etc. It should have made me really sick doing that but it didn't.
What I did find in my "adventure" was go with your vehicle, do not try to stay stiff or not move. DO NOT move your eyes with the screen and not move your head. Move your whole head where you want to look, again go with the vehicle movement. The technology they have created with the vehicle and floor moving in sync with the movie should keep you from getting sick. If you fight the movement, even just head movement, you could find the screen blurry/warped. It immediately stopped when I moved my head.