_ds_entity_info_alter(), custom view modes are defined by:
$view_mode = array( 'label' => check_plain($view_mode_value->label), 'custom settings' => FALSE, );
I am using panelizer-7.x-3.x to allow users to customize the layout and content on a view mode created with ds, and panelizer requires
'custom settings' = TRUE. If there not a reason for it to be FALSE, I would like to propose changing the value to TRUE to allow support with panelizer out of the box.