Anyone with a made flush here that isnt Q, K, or A high, is probably going to bet the flop from any position to try and get the people holding the Q K or A off the hand right there. Anyone with 2 pair, a set, or better is going to do the same. Thats why in late position i like to take advantage sometimes and bluff representing one of these types of hands (if it is checked around to me), and give whoever is drawing for their big flush bad odds to do it with. At this point, you might as well be ACTUALLY holding the set or 2 pair against their draw. If the 4th suited card comes on the turn or the river, you're beat. If it doesn't, you're gonna be able to get the guy to fold.

The only time this play doesn't work is if someone actually caught the huge flush and slow played it, or you get some foolish guy calling down with top pair or something dumb and doesn't realize how many hands can beat him. The times that you get paid off from people drawing will pay for these few and far between times that someone makes the big flush on the flop. Bluffing these flops from LP is a play that will pay off in the long run if you do it right.