Remove checkbox when integrating into Sonata #19

I couldn't manage to get rid of the checkbox when I use this bundle with Sonata as part of child form.
Being specific, if you want to remove that checkbox, usually you add sth like:

->add('logo', 'sonata_type_admin', array('delete' => false, 'label' => false, 'btn_add' => false))

in the parent form. And then, in the inner form, the one specific for the image:

->add('photo', 'iphp_file')

But that doesn't work. Any idea? Thanks