Got a read? Does he bluff? Call too much? What range of hands do you put him on? Do you think he's probing you with the flop bet and may make a move on the turn if you show weakness?

I think a slow play or weak bet trap here is very warrented, but hands like this are 99% reads. Sure, he could have the flush draw, but it was heads-up to the flop and worst case you have outs. Also, consider that with position he can't check behind on the river, so you have a full 3 shots to get the most money out of him.