document how to use hook_views_default_views_alter() to add fields to default views

I'm trying to use hook_views_default_views_alter() to add fields to the view defined by another module.

I've tried:

1.
$views[$view_name]->add_item('default', 'field', $table_name, 'edit_link');

-- causes an out of memory error (on 256Mb)

2.

    $views[$view_name]->display['default']->handler->options['fields']['edit_link'] = array(
      'label' => 'edit link',
      'id' => 'edit_link',
      'table' => $table_name,
      'field' => 'edit_link',
      'exclude' => 0,
      'relationship' => 'none',
    );

-- seems to do nothing

3.

    $fields = $views[$view_name]->display['default']->handler->options['fields'];
    $fields['edit_link'] = array(
      'label' => 'edit link',
      'id' => 'edit_link',
      'table' => $table_name,
      'field' => 'edit_link',
      'exclude' => 0,
      'relationship' => 'none',
    );
    $views[$view_name]->display['default']->handler->override_option('fields', $fields);

-- out of memory error, it appears theme_status_messages() is full.

What's the correct way to do this?