I have seen some discussion about the tire model used too, and agree that our tires are not quite up to par. I've got a friend that does a little racing, so I'm going to see if I can get some information from him or one of his crew guys concerning tires.
Information about drag and downforce values would be nice, too... I've got no idea what sorts of values make sense for different cars, and they affect top speed and handling quite a bit.
I'm going to try to sort out for myself what sort of affect these are having within the Vamos engine. Basically, downforce, when balanced will always have a stabilizing effect on the car. But too much on one end or the other can result in some very erratic behavior, as it will loosen the opposite end up. The only *real* problem is determining the amount of drag created by a given structure. Anyone got a wind tunnel?