Even though the brakes on the Savage/S40 are merely okay, at least the rotor is relatively light — and lighter than the the one EBC makes.
As you can see, the EBC rotor has more material. I don't know why that is, since the pads don't rub there. Maybe it adds to rigidity or heat dissipation or something.
I have an old rotor off a GS550. It's about 50% thicker and 3/4" larger in diameter. It weighs 6 pounds. What a lump.