Well, I ended up chosing NRT out and HKG back for SFO-SIN, simply because while neither of the overwater legs were available in NC, those two routings gave me confirmable NC for each of the shorter Orient legs at the time of booking, and were the only way to get it. In the event, SFO-NRT and HKG-SFO both cleared the NC waitlist for me about three weeks preflight. So alls well that ends well. A very good reason to keep 1K status, I'm thinking....