They won't properly fit a CS. With OE tires (which will fit the fronts just as they do on the OE rims), the front tires will stick out 14mm farther because the offset is 14mm less than on the OE rims. Thus, in cornering the tires may rub at the fender lip. If so, more negative camber might prevent the rubbing. Spacers would only make it worse. The rears can be made to fit with the right spacers because the offsets are greater than on the OE rims. The 265 wide OE tires will fit on a 10" rim, but you might want 275s instead. But if you worked all through that, you'd have a bit more stick in the rear, with the same stick in the front, thus adding a bit more understeer. You may not notice this change unless you corner hard. Rims that are 8.5" front and 10" rear would work better, even with the OE tire sizes. Apparently Porsche thinks the 8 and 10" front to rear stagger works better on 911s, while the 8.5 and 10" rims work better on the CS. In short, one may get those specs to work out okay with rear spacers, but they may not work as well as the OE setup, and certainly not as well as 8.5 and 10" rims with the proper offsets.