Maybe I didn't do much of a good research but I did not find much information on the roof cargo box. Anyways, I purchased the biggest cargo box you could buy for your C63's roof and let me tell you this thing is much bigger that what I thought.

Price- Expensive for what it is. MSRP is $694 for the XL box plus $304 for the rails
Installation- Not difficult to assemble if you are trained but it took 5 technician to install it from scratch. I guess the dealer that I ordered it from (Mercedes of Boerne, San Antonio TX)never installed one because there were 5 people working and learning(reading the instructions). Once they were done they told me that my installation was actually like a "small training" for all the technicians involved.
Capacity- This thing is absolutely gigantic (450litres of volumen), thjat is as much as the rear trunk space so in other words you are getting double the capacity. You can fit two people inside.
Quality- I was not impressed at all, the box is made of ABS plastic(molded plastic), It probably cost like $15 to build, maybe $40 if you count the two small 10" gas shocks to help the upper deck to lift.
It does not come with a simple handled so opening the deck sucks. When you try to push up the box acts like a big suction ballon and it is difficult to open the box..no handle at all.
Rails- This is a total different accesory. They are pricy but definately well built. It comes with 4 set of keys(for the plastic covers) and they easily fit. The fitment is very solid and once installed it doesn't move at all. It comes with a built in tool so no special tools required.
Driving experience- This large box generates plenty of turbulence and noise. You can hear the noise from the cabin while driving but I guess that this is with just about anything on your roof. Needless to say that the box block the sunroof view and if you lean your head forward while driving you can see the tip of the box.
Looks- The box looks strange on top of the car because its supersize but you can tell it is an accesory built for that car and not a generic Autozone plastic box you buy for cheap.

I will post some pictures soon(within the next few hours). I suggest you also look at another brand(Thule) however be awre Thule has even higher MSRP prices.

Honestly, I was hoping for at least a fiber glass box/container for that price. This box has a cheap look and just like I said before it feels like a $20 storage box that you buy from homedepot or Walmart, it just has a few Mercedes stickers and two internal gas shock otherwise Mercedes Benz is making a large profit.

 

Here are a couple of pictures that I was able to reduce on size. I hope this helps to give you a better picture of how big this box really is. Don't let the picture foul you, the box is massive(84" long) some 7 feet long. No ***** but you could throw a pillow and you could sleep there comfortably..

 

I'd leave that thing on there all the time.

As a matter of fact, I'd go to the track with it on just to baffle people.

 

Did they mention the weight rating of the roof racks?

I am tempted to buy the racks and put on a roof top tent for camping (for those of you that dont know what is that, google it)

I'd need them rated to at least 300kg.

 

Remind me again why you got this thing and didn't just use the trunk space or the family minivan?

 

Are you serious?, first of all, I don't own a Van or Mini van. Secondly if I purchased this roof box is because when I travel I carry family and luggage that exceeds the volume capacity of the trunk.

If I follow your ideology I might as well just buy a used Ford Econoline for $4000 that seat 15 right?

Like I said, I purchase this accesory for long trips or special ocasions, you might have people that carry skies, or fishing gear or golf gear. What made you think that I am not using the trunk space before using this box?

 

I think that the plastic box is rated for around 100lbs or maybe a hair more. As per 300 kg on the rails I seriously doubt it, they are robust but wouldn't carry that much weight, they are made of aluminium but I will look into it.

You will be much better off buying a small trailer just for sleeping something likme a 9feet long or so. I am looking into buying a small (no more than 12 feet long) RV to tow with the Mercedes.

 

Ok now I remember...makes total sense now.

 

Its called a rental. You rent a truck for $200 for 4 days for the family excursions. For the price you paid thats 4 trips this year alone. Plus you will get better gas mileage than you will in the C63.

Meh, you would have to hold a gun to my head before putting that thing on my car.

Just my opinion, don't be offended. If it works for you then enjoy it!

 

Posting my C63 roof box project here so that it's all available in one place in case someone is looking for this information in the future.

I went with the OEM MB roof bars and a Thule 18 cu ft Evolution cargo box. Couldn't be happier with the results. Roof bars do not make contact with the paint, are quick to disassemble and put in the trunk. Wind noise is noticeable, but mpg seems about the same. LOVE the setup!