Follow these links for modding tutorials from ISI.
rF2_Packaging_Tutorial.pdf
rF2_Track_Technology.pdf
rF2_Packaging_Tutorial.pdf
rF2_Track_Technology.pdf
By the way my G27 is set between 540 and 900 depending on the car. Changing that setting affects what ratio you use. In addition, at least the megane also has a in game steering range. I am not sure yet how it interacts with the logitech one but playing with all these settings made the game a lot easier to drive and more realistic.
I hope this helps anyone with a G25/G27 wheel.
I recommend the above logitech profile settings for all your sim racing games. All you need to do is change degrees of rotation to your preference for games that don't adjust that in game.
Games like rF2, LFS, netkar Pro and iRacing set degrees of rotation in game automatically depending on what car your driving.
If you make sure "Vehicle Set" is set to green you don't need to set degrees of roation in the logitech profiler as rF2 will automatically set the rotation of the car you are driving in game.