Moving Pile

[MI Official]

Our Crew has discussed this numerous times this season. So I justthought I would throw it out to the board here.
A is running the ball and B is clearly trying to"strip" the ball from A. At what point do you stop the play if the runner is still making progress while B is content on trying to get the ball. Additionally, As U I assume that I would be looking for anything cheap in the "scrum" as well a possible turn over, how would you signal to the wingmen if a turnover had occurred and the defense is heading the other way, other than a bag, which can be hard to see if the wingmen are trying to determine if progress had been stopped or not.