I got 30mm spacers from a place called Sixity Auto, they have lug nuts and Loctite to hold the spacer to the hub and then offset studs to mount the wheels to. I've run them for a few months now and have had zero problems. A lot of people hate spacers but I can't afford new wheels so they work fine for me, I wouldn't track on them but for a street car they seem just fine.
30mm brought my factory wheels flush to the bodywork, for S550 stuff I'm not sure though. You can see pictures of my car if you look up my posts, I'd link them but I'm on my phone.