Why do custom fields on Membership not pre-load when a member is renewing
We tried the suggestion to 


  hack /srv/www/yfnz/yfnz.fudev.co.nz/sites/all/modules/civicrm/CRM/Contribute/Form/Contribution/Main.php
  line 33 $removeCustomFieldTypes = array('Contribution', 'Membership');
  needs to be changed to be $removeCustomFieldTypes = array('Contribution');


and it did what we needed.