Hi there!
I have read the log and I have one suggestion to make related to aerodynamics.
It's about ground effect in cars that have diffuser-flat bottom. The actual physics doesn't mind the height between the bottom of the car and the ground.
The ground effect is similar with a very high setup and a low one. This isn't real.
The less space there is between the bottom and the ground the more downforce you generate.
On the other hand, if the bottom of the car touch the ground, the diffuser-flat bottom stops generating downforce and even worse, part of the weight of the car rests on it, wich results in high understeer.
I think this isn't too difficult to simulate. Just taking some reference points of the distance between the flat bottom and the ground...