Simple_form_for how to create columns of check_boxes in a do loop

So I have multiple panels in a bootstrap grid, in this panel I have a multitude of check boxes for which I would like them to break up into multiple columns about every eight check_boxes. How can they be broken up?

.container.col-xs-14.col-md-4.col-lg-6
    .panel
      %h3 Stuff:
      = simple_form_for @member do |f|
          = f.association :items, as: :check_boxes