I seriously doubt the rear springs are 560Lb considering even a very stiff front spring would be 400Lb
maybe you should take some measurements and work out the exact rate with an online calculator
Edit: and just to add, if the rears are 560Lb that would make the fronts 850Lb if it was set up with the correct front to rear ratio.... not even the V8 supercars run that high a rate, and it would make a 1000Kg car virtually undriveable