If I wanted official policy, I could look that up. I was after folks actual experiences with Singapore airlines. If you have not done this (or observed it working / not working in practice), or are not an employee of Singapore airlines, you are likely not in a position to add value to this thread. We have done this probably on ~ 10 airlines, and 75% tend not to care. 2 people in a seat is an entirely different issue, which would also violate FAA, EASA (and other) regulations, not simply airline policy.