[Harv72b]

The problem with this line of thinking is that the most overplayed hands by very loose players are suited junk hands. And a player's VPIP alone tells you nothing about his postflop play; I've played against people with VPIPs above 50 who were actually pretty good postflop players.

Assuming you have a decent amount of hands on the villian (at the very least 50, preferably a few hundred or more), you want to be looking at his postflop aggression level, and in particular for this hand, his river AF. If he's normally very passive postflop, then a river raise when a flush draw hits would worry me into calling. On the other hand, if his river AF is through the roof (indicating that he likely tries to buy a lot of pots by raising/betting scare cards), the 3-bet looks good.

If you don't have the statistical database to make a firm read possible, then just taking notes on hands like this one will help in the decision-making process.