Wow, what a roll up, New record.
I've added more slots for sign-ups, we aren't restricted (at least I don't think so) in numbers.
Re these cars, I haven't tested them much at all, but i have tried each car at Noiker (gravel) as well as driving a few at random when making the promo movie. The handling varied a lot and I found some to be very touchy regarding braking (downhills at Noiker was murder). This can be fixed by adjusting the brake bias towards the front. Go into the car setup section (Tune Car) and under brakes, adjust the pressures for the front and back to get them more like 70/30. It should help a lot.
Re handbrake turns, haven't tried much yet on tarmac (they spin easily on gravel) but try entering the turn a bit faster as you hit the handbrake. You should start the turn in first, then grab the handbrake, but keep some power on through the turn and especially the exit. I suspect you need to be more aggressive with these. You could also try increasing the Steering Lock (again under set up) for tarmac, I have found it helps a lot. With increased steering lock, you can even avoid the need for the handbrake with a bit of left foot braking and some aggressive power sliding on exit.
Spinning them around on gravel or snow is rather different (especially with the brake bias on some of them), they spin very easily.
I think we are all learning about these cars, they are different, but I am finding them a lot of fun.