Hey, Lawson:
Here's what I've used in the past:
//Create the new form
XDocument newForm = thisApplication.XDocuments.NewFromSolution(@"C:\Users\Lawson\Desktop\Switch View.xsn");
//Convert to IXMLDOMDocument2
IXMLDOMDocument2 newFormDom = (IXMLDOMDocument2)newForm.DOM;
//Set the namespace (correct for the appropriate namespace for YOUR template)
newFormDom.setProperty("SelectionNamespaces", "xmlns:my=\"http://schemas.microsoft.com/office/infopath/2003/myXSD/2008-07-06T22:11:15\"");
//fill in new form fields
newFormDom.selectSingleNode("/my:myFields/my:WhateverTheRealXpathIs").text = "Test";
You'll want to update the namespace. You can set fields in your new form to values from your current form rather than the text value I show.