subform

This, in the [#post] array of $form that resulted directly from drupal_execute, makes it look like it would be so easy to modify before final submit:

damn. action_group_node_form, the form that is an organic group, has none of its organic group-iness when pulled up through subform.

The trick-- and it is tricky -- is to specify your node type not just with the agaric_example_type_node_form but also in the arguments, 'type' must be set to agaric_example_type.