Thanks everyone for the tips

I called SQ and indeed the FF# had not made it into their PNR, but the nice agent was very happy to put it in. She also agreed that *G status would put me on a priority waitlist, and she said she'd put in an SSR to SIN to get that w/l cleared (hasn't happened yet, btw). She also was happy to put seating preference requests in which was nice.
I'm quite looking forward to trying SQ again on SIN-CPH in the 772 - it's been a few years since I last flew them so will be interested to see what it is like.
Oh, the agent also put in a exit row request for me. Obviously I've got buckley's of getting it, but it can't hurt.
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RichardMEL, UA 1K
A Star Alliance Member.