Whilst I have a small capacity for alcohol, I have always found that FL39 has the reverse effect upon me, as reported by others. I can take MORE alcohol at altitude than at ground level. I've not tried to test this to the ultimate but after 45 years of paxing - well, 36 as an adult - I know how much I can have on board.
I'm always careful about drink and the last time I had a hangover was July 1976. But it was a REAL hangover. I got smashed on the Saturday night and still had a headache the following Tuesday morning ... so I decided not to repeat the event.