Sorry, I thought this would be about a tandem seat airplane with dual controls. Yes, if that, no if the PIC is not seated at a "pilot" position with full controls. I was asked by PIC in the back seat of a Cessna Bird Dog, I declined, as there is not a full set of controls there. I was asked to be PIC in the right seat of a Cessna Caravan, and after review, I agreed, as the flight manual reference says: "One pilot required in the left seat", and the other guy was a pilot, so I could be PIC in the right seat. I couldn't be PIC in a back seat in a Caravan - nor a PA-28. Really, If you were a pilot in the back seat, and the pilot in the front seat crashed, would you still be willing to sign as the PIC for the flight that was crashed out of your control?