Kelvar, providing the front end suspension isnt rock hard, the softer sprung rear suspension should help the car turn in (providing the tyres are up to it).
Because you have even suspension settings, its not allowing the front or rear of the car to react differently than the other, hence the neutral handling...
Might be an idea to look at your droop / roll centre too
If for example you try a red tamiya spring on the rear of the car, you should see the difference straight away. The only "problem" is to prevent the car from scrubbing its speed off through the corners by allowing it to "dive" or work more with the weight transfer, hence the suggestion to look at the droop/roll centre too
Obviously, it depends too on how you prefer the car to feel in the infield
Try it in some practice time and you'll soon see what happens with a softer rear spring