As long as SSR field shows as HK, holding confirmed, a trip to the airport authorizing and signing an auditor’s coupon is totally unnecessary. There have been numerous threads on this topic. I have been told by a number of very seasoned CRSs.

If you really want to be on the safe side, while you are at the airport, ask CSR to note in the United Field that you were there at xyz airport, showed your ID and authorized the transfer of the upgrade instrument.