Thanks for the reply Josh - I think you missed understood my requirement though. I am wanting to put some of the progressive fields above the non-progressive fields (not arrange the order of fields within the PP group) as it seems that the progressive fields are always the last.
I've managed to do it using Javascript/ JQuery anyway - here's the code in case it helps someone else/ anyone has better ideas:
<script>
MktoForms2.loadForm("//app-sjg.marketo.com", "572-XMB-986", $MarketoFormID, function(form){
var MarketoForm = form.getFormElem();
var FormField_Contact_Message__c = MarketoForm.find("textarea#Contact_Message__c").parent().parent().parent();
MarketoForm.find("div.mktoFormRow:last").after(FormField_Contact_Message__c);
});
</script>
Not ideal but I'm stumped on any other way...
Cheers
Ben