[Plugin: Taxonomy Widget] Cloud

You should be able to specify arguments to be passed to wp_tag_cloud() using the 'mfields_taxonomy_widget_args_cloud' filter. Something like this should do the trick. Add to your theme’s functions.php:

add_filter( 'mfields_taxonomy_widget_args_cloud', 'my_tag_cloud_args' );
function my_tag_cloud_args( $args ) {
    $args['smallest'] = '1';
    $args['largest'] = '3';
    $args['unit'] = 'em';
    return $args;
}

No problem! You help me realize that putting those custom filters in the plugin was a really good idea 🙂