Alter Ubercart Billing/Delivery Panes with User Profile Info
The billing/delivery address panes are driven by a custom uc_address form field. You need to alter it's #default_value object to alter the fields.

For example:

$form['panes']['delivery']['address']['#default_value']-&gt;delivery_first_name = $user_fields-&gt;field_name['und']['0']['value'];
$form['panes']['billing']['address']['#default_value']-&gt;billing_first_name = $user_fields-&gt;field_name['und']['0']['value'];