Tested it with Logitech MOMO FFB Racing Wheel as well, now, and it still works great, better than the default. Strength ingame 100%, driver control panel 150%.
Maybe some values can be tweaked a little bit more to make it even better.
I had a look into the FFB effects file myself, but there are so many values and I don't know how I have to tweak them (+/- and ranges). Does a good explanation exist somewhere?
By the way: Some rumblestrips have no FFB in the game, do they?
For example in Melbourne. Sometimes I'm missing some FFB effects.