RCS of a non stealth fighter is not at all a concerns now. None of the existing lo aircraft will have a chance against the existing stealth fighters in BVR, and in case of non stealth dual more than RCS the EW duite, situational awareness, a2a missile & aircraft's kinematic performance will be the deciding factor.F15EX has also the RCS of a farm door ! (as Su30MKI : a big radar, with big range (specially for the F15 AESA one) but a poor stealth feature)