Want to get rid of your understeer at the autox then you need some more negative camber and scratch the 235/265 tire setup. You need a square setup. Your car is almost perfect 50/50 front/rear weight balanced. Having a 235/265 setup is almost guaranteed to give you understeer no matter how much negative camber you dial in.
My recommendation is the dinan camber plates plus a set of wheels with 235 all around for the autocross track. The dinan camber plates are not adjustable which for me is a positive since some adjustable camber plates can be problematic over time.