Helmet fire - for hovering over the water at night you want a second pilot up the front - not for when it is all going right but for when it goes wrong and since the winch operator is going to be doing exactly that, he is no place to help the handling pilot deal with a malfunction when winching. It makes the difference between managing a malfunction and ending up as another casualty. SPIFR, no problem - in the cruise the rear crew can help out as much as they like (unless they are giving CPR in the back to a critical casualty) but over water ops, give me 2 pilots every time.