Well, if you think your opponent has a bigger flush, than that means your drawing specifically for that straight flush, so one or two outs depending on whether it's a gutshot, or open ended...
So, no. You should probably get away from the hand.
if hes slow playing it and letting you see free cards keep checking lol.......but other then that(I see this all the time) dont call huge bets to see your inside straight flush draw its only one card in the deck. 2 cards for your open ended obviously