One tip - in AMM don't go to the normal check-in, but go to the "Crown class check-in" - available also for OW saphires and emeralds. It's in the same terminal, easy to see when you get out of your cab. Very pleasant and personal service, unlikely to kick up a fuss.

You also get your private passport controll and security check* - after that just walk up to the regular immigration window (Diplomatic line has no queues) and just say "already stamped"

* scarily light, I could have brought on most unmetallic anything...