Hello~
Is this a DONE or a LONE? With a DONE you probably want to avoid the CX if you would like to sit together especially with their new herringbone config~ That's what we'll be doing!
Just with routing, you might want to do NRT-SIN-HKG, isntead of NRT-HKG-SIN, to make it 41241 instead of 40530 miles
You might want to put down a list of the destinations you actually want to visit, so people can adjust your itinerary to give you more miles!