Replying to Protecting dem knees

So i was up at PC this past week and witnessed my brother tear both ACLs doing a 3 on a park jump, we have not come to a conclusion on why/how it happened (DIN too high, loose tendons, heavy skis...was on a pair of 2014 line opus, etc.) but we believe that the DINs were way too high...13 I think. My question is this, what is a good DIN to be set at while not absolutely destroying your knees but also a perfect medium so they arent popping off every 5 minutes?