OK

[tipperdog]

The answer is call and it's not close, assuming that villain is a "excellent" post-flop player as OP indicates. Incidentally, this is almost the exact situation Barry Tanenbaum described in a CP column called dangerous river raises way back when. I remember this article so well, because I was the student who submitted the hand!

Incidentally, BT's conclusion (after arguing you should call-down with the A-high flush) was:

[ QUOTE ]

Yes, many of your opponents will make fun of you when you win the pot by simply showing down the nut flush, but you will still have made the proper play and do not need to educate them. Be glad they have the wrong impression of you at the poker table.


[/ QUOTE ]