PW F100 ?
Pedant : Counter/rotating is different than Contra/rotating?
JFZ90 I heartily apologize; the RollsRoyce Trent data I nicked from a Puff brochure. It very definitely referred to the TRENT's development as having made possible some diminution of ambient heat surrounding shafts, bearings, etc. If you demand proof, I will seek it out. Other than a "Paraphrase" of the brochure's text, the data is accurate, and even though a sales pitch, it needs be a valid claim. No numbers were included. Some things I accept at Face.
At long last, a picture of what "Aft Migration" may have accomplished, and a glimmer of the Splines face(s).
cheers, bear