[ungarop]

This isn't a tournament. Big Stack does not have to show his hand immediately when calling the all-in on the flop, even if asked.

After the river if the Big Stack wants to claim the pot he/she will have to show the hand (as indicated by the floor).

If someone in the hand invokes IWTSTH, then he is required to show the hand (by rule).

Since IWTSTH has been used before, I call the floor while protecting my hand and ask who they think I am colluding with. If the floor rules I have to show my hand, I show.

If IWTSTH had not yet been used, I ask the player who they think I am colluding with, and then show my hand. The second time, it is in the muck before I show. The third time I call the floor. Unless it is a great game, I've likely changed tables after the first time if I recognize there's an IWTSTH nit that's going to put me on uber-tilt.