Keep It Tidy, the FI is worked out against Sortie profile Codes, the R1 and MR2 fly totally different profiles. R1 - mainly low-high-low like a civvy airliner, MR2 - all over the shop, literally! Even some of the engine internals are lifed completely differently dependant on which airframe variant they are fitted to, to the extent the engines have a different mark number even though they appear almost identical in every visual respect.
On the subject of AAR and fuel leaks, Here's a theory of mine to kick around. I wonder if anyone has considered this:-
The pipelines in the bomb-bay will no doubt have been constructed from a material having a similar thermal expansion coefficient to the airframe they are attached to, but what happens when everything is in equilibrium and suddenly there is a change of temperature (and hence dimension) due to the high flow rate of fuel at potentially a considerably different temperature to the airframe....? Is there sufficient flex in all the FRS coupling seals to allow for this dimensional change? Is this why the leaks never seem to be reproduced on the ground? I reckon the old MOD700(?) standard of AAR system with the rubber pipes snaking their way through the cabin was better in this respect, apart from their being located within the cabin, obviously. I sometimes wonder if replacing a fair length of the metal AAR pipework in the bomb-bay with aeroquip would be the proof of the pudding??