Params
Example
$elements['test_radio'] = array('type' => 'radio', 'label' => 'Test radio', 'text' => 'foo');
To set a radio button as checked in the constructor use:
$elements['test_radio'] = array('type' => 'radio', 'label' => 'Test radio', 'text' => 'foo', 'attribs' => array('checked' => null));
We realize this doesn't make a bit of sense but you will just have to live with it.... AHHHHHHHHHHHHH!!!!