Recommended camera load:
SliderPLUS X Long: 22 lb (10 kg) or less
SliderPLUS X Short: 30 lb (14 kg) or less
Wing Pro: 48 lb (21.7 kg) or less
SliderPLUS X series has a wider body which provides increased durability on a tripod under heavier camera loads. SliderPLUS is a manually controlled slider, however, you may motorize your slider with the help of the Slide Module.
On the other hand, Wing Pro is another manually controlled rail-less slider which would absolutely carry your Sony FS7.