Hi Pablo,
When I did the files on airlinerperformance they were based upon the flight models from the various developers, which are normally specific to one engine type, rather than the visual models which probably do cover all the engine manufacturers. To my mind there is no point in making a file for Roller engines if the flightmodel is based upon Pratts - I'd just wind up with a load of complaints about how my file differed from the sim (maybe there's a poll to be had there - how many simmers actually compare time and fuel used versus plan, and how many simmers actually use an OFP as it is used in the real world?).
Which 777 are you flying and I'll take a look again? From my very limited experience RR engines burn about 3% more than their PW equivalents and are heavier, but again if it's a PW-based flight model.....In such a case changing the aircraft details is a suitable way of covering different variants in the sim.
To answer some other earlier posts:
On the DC-10 I'll upload my old files, but I was also most ways through a new version with many more cruise speed schedules - will see about finishing that sometime.
There is a Twin Otter file up on www.airlinerperformance.net
Cheers
Jon