SASless - between them I think wobble2plank, Gordy and John E. have answered your questions better than I could. 'Ownership' and 'licenced to fly' a type are not the same thing and I think it could be argued that if you are flying IFR whilst yet to qualify then the IFR qualified pilot is the PIC, if it is just practice then the other pilot could also be known as a 'safety pilot', assuming the pilot flying does hold an IFR rating. That is the best I can do, I think the military sometimes have a better approach to this subject than the various regulating authorities.