Hello there, I'm see you have a problem with 'car id' slots?
In my opinion, the development of the project (carpack*) was to be in the other direction, well, what can you do? And to add new cars i'm propose a different solution (my experience can be of useful):
So game have 3 same cars (VPE show way to one car model):
id383 - Koenigsegg CCXR Edition
id609 - Koenigsegg CCXR Edition "Solar Crown"
id626 - Koenigsegg CCXR Edition Racing School Asphalt
3 SAME CARS CAAAARL
this cars have mirror car id slots (in direct dependence on the original model)
So, how to use it? - easy , I'm have implemented this way in my 'extra car pack' (my site aliceredinger.blogspot.co.uk), for example game have 2 MB ML63 AMG: id375 (original car) and id637 (mirror car), i'm replace mirror car to MB g55 AMG (model based on ml63, not need create spec) and not lose nothing, just add new car, same way with other cars (If you are interested in this method, you can see my site)
Known bugs for future patch 1.7: Pagani huyara - sound in the garage, bmw 9000r and Ferrari FXX - no gauges