Believe it is correct to say that only the Rolls Royce RB 211 powered B747-200's could tank extra fuel by utilising the 2 and 3 reserve tanks. The shorter length of the 3 spool engine kept the turbine disc area clear of these tanks in the event of uncontained turbine failure. Enabled CX to help fly non-stop HKG/YVR in the Kai Tak days. I also believe the B732's had reinforcing plates over the tanks for protection. Comments of course, most welcome
Terry