As an F/O I saw the Captain RFO scenario play out several times. First of all it was mainly a handful of very senior Captains who would fly these lines so I would see them on a regular basis. Some of the Captain RFO's would be very diplomatic and show up as a team player. However there were a few who would show up in Paris Ops, Osaka, etc. and just walk up and announce that I'm the PIC and change the FPR to reflect that this is my operating leg. Sometimes on the last leg of the trip this would take away the F/O's last landing for the pairing. You have a crew that has been flying together for several days to possibly over two weeks and here comes a Captain as RFO who stirs the nest and possibly adds tension to the cockpit. The CRM on some of these flights has been less than exemplary to say the least. As I previously mentioned some of the Captain RFO's were very diplomatic but several others were not and it was to the detriment of the crew operating that trip.