I was wondering, are CO passengers allowed to sleep on the floor during a flight?

I've often been on long flights in cramped Y seating where I was so uncomfortable & desperate to sleep that I thought seriously of stretching out on the floor (between the seats, not in the aisle, of course!). (For example, when you & a family member are sitting in the middle 3 seats on a 777 or 767, and the middle seat is empty. The family member lies down on the 3 seats and I would sleep on the floor.)

Aside from the health concerns of being in contact with the whatever was last spilled on the floor, is this simply frowned upon as bad manners, or is this really not allowed for safety reasons (since you're not in your seat with your seat belt on)?

Does anybody know if there is official policy on ths or been discouraged from doing this?