Setting fontSize within core/heading

Trying to specify a default font size. Using my markup below, typography is ignored and therefore fontSize is also ignored. Is there no way of specifying these parameters as default on an innerblock?

<?php
array('core/heading', array(
  'level' => 2,
  'placeholder' => 'Title',
// following is ignored: 
  'typography', array(
  'fontSize' => 'Small'
  ),
)),
);