Nut flush draw in 3-bet pot with two all-ins ahead of you
This is a spot I've been wondering about since it comes up on occasion. The exact details of the hand don't matter, but say UTG raises, and almost everyone calls. You call with A9 of hearts from the cutoff since it looks like a nice family pot is building, the button + the blinds all call.
Two hearts come on a Jack-high flop, UTG open-shoves, fold, call from MP, then folds to you. Alternatively, UTG c-bets big enough you know he has an overpair and is going to jam if reraised, and MP does in fact reraise. If you flat call, UTG will shove, MP will call, and you will be priced in to calling as well. Same thing if you come over the top. You have no guarantee if the button or blinds will call.
Mathematically, I know the call is correct even if they both have monsters. With ~35% equity I need two other players to be all in order to make this a slightly profitable call.
With 3 players all in, I would force myself to call, but I usually end up folding because I haven't invested too much in the pot.
To get to the point, my question is: How much do you play according to objective math? Do you call in this spot with the naked nut flush draw?