First, you did and still do a great job with this plugin! Thank you!
Second, is it true that the autoresize for cross-domains only works to enlarge the height of the parent and not to shorten it? Unless you reload that parentpage again...
My dummy-site you can find on http://www.edwinkonings.nl/test/, where the parent indeed is resizing the iframe from 1500px to 3000px and even to 5000px, but then back to 1500px the parent stays the same as to 5000px.