you should not need any shim/spacer for the caliper. I bet the spacer thickness of 0.5" is not correct. you should compare the thickness of the rotors to calculate the right spacer thickness, not the "hat height". assume the thickness of the rotors are the same at the hub mounting area (not the braking surf; the area where four holes are), the thickness of the spacer now should be ="the new rotor thickness" - "the old rotor thickness", and then divide the result by 2. if this still can't get your new rotor center inside the caliper, you should mount the caliper (without pads) and the new rotor in place, then measure the offset. the offset should be the distance betwteen the center line of the rotor (the center between the two disc surfaces) to the center line of the caliper. this should be the spacer thickness that is needed. hope this is not too confusing. i think you should be able to figure it out anyway when you are installing. I want to do it, but it will cost me around $150 to get the remanufactured ones from Kragen for both sides.