Quote from Scawen :

I don't think you have read the thread. So I will write again : These things are available on the formula cars already with no HUD displayed, and will eventually be available on the GTR cars as well. Also I have just provided some script files so you can do it right now with no HUD visible.

I had read the thread but I was under the impression that the sequence F11, Down, Right, F11 doesn't work with Shift+F on. I was sure I'd tried it and it didn't work but I just tested it and it does - sorry about that.

Thanks Scawen. That really works well for me now.
I just changed rear arb in 5 steps at once.
arb_r.zip
That's why I like this game and the devs. If you have an improvement suggestion they read what their customers want and if it is possible they help immediately. That's not usual but seems to be a normal thing here.
That's why I will also preorder S3. This game maybe developed step by step but the users have big influence on how it is developed. I hope this will also be the fact in future.....