thx Tiger!!
that's good advice! saying what I should/coild AND explaining why. Now at least I learned something
At the end of the training-session, I also tried on some old Foam-tires I had in my box. Those tires were very wide and I had to reposition my rear schock a bit, going "one hole" more inside on the A-arm.
The car was much better in balance then. I thought it had to do with the Foam-tires but it might also be due to the changed Shockposition. AFAIK, a more vertical and inwart position of the shock should make it softer.
Good point about the oil also. I would never have thought about that.