Quote :

about threats on Internet forums from anonymous kiddies that take themselves a little too seriously...

Peopple is not taking it too seriously, it's that some peopple like you are taking it too lightly

Quote from Karoti :

I must be thick as I can't see how this works... if I assign a setup to an ai, it changes for all the other ai cars.

What am I doing wrong?

Add one AI while having chosen the limited setup, then go back and change setup, and assign the rest, etc. Just like you'd do if you want to assign different cars.