I have just released version 1.02 of Suffusion Shortcodes with a minor change. Earlier the [[suffusion-widgets]] shortcode was not respecting the container-class parameter … because shortcode parameters cannot have hyphens in them! I had overlooked this several months ago when I introduced the functionality and it only got caught today. I have fixed this error in version 1.02.
Note that you have to specify container_class='custom-class' instead of container-class='custom-class' (note the underscore instead of the hyphen).