Its a bit of a tough one at the moment. Using 270 degrees is obviously unrealistic for road cars. There is no way a real caterham or normal road car would get 36 degrees of wheel lock to one side with 135 degrees of steering wheel lock. In LFS they graphically do 720. Even a real caterham could well use more and it seems that 900 is about the minimum for more normal road cars from my admittedly limited experience.
Now there are loads of videos that show that in real life, with most car geometries (caster angle etc) the front wheels will automatically want to go in the direction the car is moving, even if the car's back end steps out. So this will often apply opposite lock for you! Now with a DFP at 900 degrees setting, it WILL do this.. but at about 1/10th the speed you might witness in a real car.. Hence its way too slow and you'd have to try and force this, making the wheel scream like a pig.. This would be unrealistic and unrealistically hard.. Now with the wheel at say 270 degrees, the realism is overshot the other way. It becomes easy (hands on at all time) and a LOT faster to steer.
So the faster the FF wheel is (and the less it resists manual steering) the more lock you can use while it still is realistic. With a DFP the best lock setting is in a 10cm thick walled safe with a combination nobody knows..
I wish I could try the G25 soon, it should be a lot nicer..
I don't use force feedback which is also a compromise, as I have to do all the steering manually which at a real 720 or 900 degrees would make drifting nearly impossible..
Sofar its all compromised by the actual wheel hardware.