Well AS / HA replies are not comforting - basically said if space is available you can upgrade yourself online, but they have no details about how or where to do that. When I booked the ticket first upgrades didn't exist so that seems to disqualify me from using certs. Seems like only option is to rebook and pay 50% more since fares have gone up to risk it. Given uncertainty Im not going to pay few hundred dollars more just to have the chance at something that there is no clear policy on.