For IHL:
You were asking about vertigo in two pilot crews
well I think there has been a lot of instances where just that happened, not to me yet, since I only fly single engine, single pilot VFR for the time being. Look at the statistics on the crashes that do occur in bad weather where CFIT is the cause, couldn't Vertico/loss of Situational Awareness be one of the issues leading to it in the first place?
Just for some thoughts anyway...
