I’ve got one of them 
NFZ freaked out and wouldn’t let me take off first attempt, I had to jump through a few hoops on the DJI site to unlock the NFZ (another reason for me wanting to roll back to .700 - which I’m going to attempt tomorrow).
In terms of legalities, I’m no lawyer but if the stadium is empty I don’t see it being different to any other type of building. Common sense is probably all that’s required 
