Yakima has a fit kit for their system. I had their roof rack on another car, so It was the cost of the fit kit to put it on my smart. I purchased the optional spreaders for my obviously longer load

. very happy with it, and I expect to be able to use it on what ever car I purchase in the future.
I've used a hitch rack before and been happy with it, but that one needed a 2" receiver hitch, so I sold that rack when I no longer had the SUV to put it on. not a fan of hitches on passenger cars anyway- I do not prefer the looks.
T