Thrustmaster has a GSC ini-file for the TS500 included -> "Game-Setting" (there is also a pdf-guide with all the settings).
works like a charm!
try to set it to 270° for GSC to get it perfect!... Rotation in 460 and T500RS working as on Gran Turismo 5.
For the question if the Fanatec GT3RS is supported by GSC.
Yes it is. I'm using it together with the CSP pedals and it works very well.
The CSW will be tested with GSC in a week or two when the betatesters start.
Around end of May to mid June the reviews will start pouring in.
I'm using 540 degrees and set the wheel lock to 22-23. If you want 900 then increase further.
For me this works perfect.
As Reto stated, you can set it directly in in the ini.
Right now i'm driving the CSW and are using 150 force, 100 FFB.
With the GT3RS i left FFB at 100.
Running default FFB settings in game.