Fair enough.
The only problem that I have with a pot size bet on the flop is the danger to lose him. You need to protect against the flush draw, no doubt, but you don't want him folding either when you have a set of kings, because really the chances of villain having 2 diamonds really aren't that high. Of course it's good to be aware that the board has FD, but you really can't come out firing big because of it. A 2/3 pot bet is perfect IMO, and that's what he did ($12 bet, pot was $19 - rake). The ideal is have him play back at you like happened here.
The amount you bet on the flop pretty much has to be consistent with what you've done prior to this hand as far as c-betting in a pot that you raised PF. If you've been betting the pot every time in that situation then you should do so again, but if you've been doing 2/3 of the pot you shouldn't change it. In this situation the c-bet could be the only action you get, cause after that he might fold when you bet the turn, so you can't mess it up and also you need to make sure you don't become predictable.