jpmon - 1:16 pm on May 1, 2007 (gmt 0)

Not exactly, but I created a lot of other small sites, that I used in link exchange systems, but for sure their content was not duplicate of mine main site. The all other small sites are not affected by penalty 31. Their PR is usually 0-2 and main site has PR6 - so it had affiliate small sites related (linked to from main site). This site and it's structure could be identified as breaking all of the google guidelines, so I'm not much surprised.

1+2 position was for more then one year.
Cause for the daily changes in the position might because just by the algorithm google uses or by google intention to not give hint for new sites affected by this penalty how to search for in google (if you do not know the name "penalty 31", then imagine how difficult it is to find proper page with google search).

If the site domain is changed, then site returns for about two weeks and gets back on the penalty. The only solution (I think so) should be to create fresh new site, allow robots to index only few main pages of it and move all content to notindexed area of new site, same time removing content from old site (or also disabling indexing by robots). After six months you can allow robots to index all pages on new site.