So I paid for an upcoming international flight (reasonable C inventory available) and promptly called to apply eVIPs to the ticket. After applying the upgrades, she asked for my credit card to ticket the inventory. When I pointed out that it was paid with gift cards, she had to call someone and cancel the upgrade transaction. According to the AAgent, gift-card ticketing has to be completed before applying the eVIP. Meaning I have to wait (and hope the C inventory doesn't evaporate). Should be OK on this trip, but it's probably worth a "heads-up" to others that seek to do the same.