I had a go in the 512 S yesterday in the challenge mode.
The AI seems to be unable to control this car and is all over the place, which makes it fairly easy to earn many RP in no time

After a few races with this car I decided to change car, because it felt almost like cheating

.
Of course if you want your 30000 RP in a quick way this might be the way to go, but I like it more the hard way.