Yep I have interchanged PEK / PVG / MNL many times. PEK / PVG as you say same miles so a monty. Inter MNL with a Nth Asia dest like PEK / PVG was diff mileage - but it could be done. If increase in pts read online easy - just pay extra pts and it would calculate extra $s read - easy. If other way and you did it online no refunds - call up and do over phone and excess pts and $s would be refunded- go figure.