May be you can try this way to get the XML before and after the Reader extensions.
1) Place a Text field with multi line allowed.
2) Place a button on the form with the following in click event.
TextField1.rawValue = xfa.data.saveXML("pretty");
3) Open the form in either Reader/ Acrobat and click on the Button. Save the XML data in a file that was assigned to the TextField.
4) Reader extend the form.
5) Repeat the step 3 again to capture the XML from the form after Reader Extensions.
This way you can get the XML from the form before and after.
Thanks
Srini