It is obvious that this thread has reached a point where someone following it has lost interest in the content being offer in it.
The answer to “How to downgrade from 1.3x" question has already been posted by Lycan in another tread:
http://forums.dlink.com/index.php?topic=5085.msg29949#msg29949 “Every time there is a Kernel update in the IPoS you will not be able to downgrade." This is what D-Link Technical Support can offer for now, D-Link's Product Managers and Engineering Departments are working on it.
For now the topic will be locked.
Thank you all for your opinions and we'll continue working on this.