If you look at AS National public races you will find 70%+ of the field (and usually more) will be FXR's. Even though the FZR, when driven well, is clearly faster. In league races I am sure the mix is very different where the drivers tend to be more interested in outright speed compared to ease of driving.
I am not sure you can ever address this so if you balance, or at least close their lap times towards each other, public races will probably become 90%+ FXR. If you give the RWD an advantage enough to see them used more in public races, league races will become all FZR.
Before we can really balance them we would need to agree on what type of races we were trying to achieve the balance in. I don't think we could ever get agreement on this. Won't it will come down to making the imbalances within tolerable margins more than any real balance. In my mind the goal is to make sure you never see one car dominate the grid.
Maxim