We went to the passholder preview last night and were able to do FoP twice. The first time the posted wait time was 60 minutes, but it ended up being about 20 minutes. And that was mostly people holding up the line to look around as the queue is so incredibly detailed. When we finally sat down in our ride vehicle a CM came into our 'room' and pressed a button that brought up the back and leg restraints. After this there was some delay and we were in this position for about 10 minutes, although it felt a lot longer. This was quite uncomfortable. I have never been claustrophobic, but I was feeling it here and was starting to panic a little. The problem is that you are completely stuck and cannot move. Your stomach is pressed against the front and the thing is pressing against your back. I had an itch on my leg that I could not reach and we had no idea what was going on as the CM left after locking us in. You're looking at a little screen that shows your face and the face of the avatar and a progress bar. The bar was stuck at 65% for a very long time.
When the ride finally started I looked around and understood why you have to be stuck. The whole room you're in detaches and moves around violently, so they really don't want you to get out of your seat. I do feel that a CM should stay in the room until the ride starts. It was just weird that we were stuck in those chairs without knowing what was going on.