I have gotten 3 upgrades cleared on the same flight (SIN - ORD, 1 stop via HKG) before, however, the flights were booked and confirmed with NC2, so there was only 1 on waitlist and seems to be the first one on the waitlist. Not sure if 1P mileage upgrade clears after all 1K upgrades (PA, PB list?). As stated, try to get the flight to ticket like ORD - HKG - SIN instead of ORD - SIN, 1 stop, which might improve chances. I have successful gotten the ORD- HKG - SIN via consolidators instead of through .bomb.