Thanks! Given the half inch difference of the rear, maybe that is why they don't call for it? Still, you'd think 5 mm wouldn't be an issue.
It could be if you think about it:
A half inch = 12.5mm. The half-inch difference should be halved on each side of the wheel, so that the wheel is 6.2mm wider in both directions.
In the rear, take the difference in offset between the Carrera S (45) and Carrera Sport (47) -- 2mm -- and apply it to the appropriate lip. In this case, the Carrera Sport's inner lip will be 8.2mm closer to the suspension, and the outer lip will be 4.2mm closer to the fender. Add another 5mm to that with a spacer to "even things out," and you're talking about pushing the rears -- on the widest rim available as OEM -- outward nearly 10mm. That's highly dubious.
Also, consider that the tire size is the same. The Carrera Sport's rear tire will be slightly more "stretched" than on the Carrera S wheel because of the extra width. If you decide to put a wider tire on that rim, you could run into big issues.
In the front, where offsets are the same on both wheels, the concerns aren't necessarily related to rubbing on the fender; it's rubbing on the suspension. Remember that a hub increases its toe-in when turned sharply in either direction. 6.2mm can make a wheel rub badly at anything close to full lock. You can probably use 5mm spacers up there fine. It's the rears I'd be worried about.