Jaklefox
sorry I couldn't sell you the 18s off my car.
I've been looking at a bunch of stuff and the above info looks correct on the spacers. The carreras take et 65 wheels and the Boxster takes et 42 in the rear.
I'd try wheel enhancement for the 20mm spacers. They are fairly expensive, but are known for top quality and OEM stuff.
As long as the wheels are 18x10, they should work fine and the longer studs should be no problem. They won't aactually put more stress on the hubs, because the center of the wheel will be back where it belongs. There will be some additional stress on the longer bolts, but the hub-centric spacers will mitigate that.
