I flew co-pilot of a Citation Mustang and CJ4. The owner was single pilot typed. We went though and did all the training for me to get my SIC type in the plane and we flew the plane as a crew. Talked to FAA about it, they said that as long as I was trained on the plane that I could log the time. The single pilot typed person does not have to act on the single pilot qualification if he or she doesn't wish to for that flight.