What's wrong with the one on Inferno? Try tweaking it like I do:
Make a copy of the set and adjust arb, steering and diff until you can drive it easily, then try resetting the set to the original in small steps.
I haven't driven the RAC much so it might not work seeing as it doesn't have a rear ARB
Good luck
Seems that you don't know what's driving a RAC like since u are a demo racer.
Of course I tried to change these settings.... RAC and FZ5 have both these understeery features
You suggest these ,for the front tires, in order to decrease understeer???
increase front psi (the opposite)
more toe out on the front (that’s going to give you better turn in so lets say its in the right direction but it is not going to give better traction to the front)
Less camber on the front (???? Again the opposite... unless you mean less positive -> more negative camber)
increase front downforce (Yes that’s the easy one but no, the rac does not have downforce)
RAC setup is a mess… the lack of rear antirollbar destroys that car.
There are enormous weight transfers at the rear suspension and this makes it really unstable when changing direction.
A less understeery set could be nightmare eg when making a sudden move to pass or avoid someone on the track.
!idea!
The inferno setup is made under patch U, there was no preload then and most sets had the coast setting straight to max to eliminate overseer while letting off the brake or when the car was coasting.
Now with the preload setting the differential resists more to the car’s turn.
Try to reduce the coast setting; it may help to reduce under steer in general when not pressing the throttle.
Try the one from squassel for Ky Nat. It's the only set I've come across that is quite manageable at turn in under braking, and having LSD it's great at turn exit under power. It's a good starting point at least - my hotlap there was done with a not-that-big mod of that set. Actually all my hotlaps with RAC were done with mods of that set.