I agree with Brad here, however being out of position I would 3bet with an even larger size, maybe 5x, to discourage any marginal hand to see a flop. I would definitely c-bet any flop in case I’m called, and decide between checking or continuing to bet on the turn, depending on the opponent and what hand I put him on. I tend to be an aggressive player, and when I 3bet and then hit I try to play it as aggressively as I can to balance out my 3bet bluffs. The problem with giving away the betting lead by checking the flop here is that you don’t really represent strength, unless you are known to make sneaky and risky slowplays with very strong hands such as aces or kings. One last thing to remember: it is really hard to flop a flush, and most of the times they’ll have an offsuit hand with a decent diamond if they check-call. I hope this was helpful, let me know what you think. Have a nice day, greetings from Milan!