Hi, could you consider adding the widget's slug-name as a CSS class within the div that contains the entire widget? That would make it a lot easier to select a particular widget in my own CSS.
There is already a CSS class added which looks like "widget_tribe_widget_builder_1178" but it would be nicer to have one that directly matched the slug-name (which of course is based on the widget's own title).
PS: it would also be good to see this plugin updated to show support for WP 3.7x. :)