Rated 5 out of 5 stars

After fixing the maxVersion in the install rdf, I got this to work partially in Firefox 4.01 (not in 4.0!) - it splits now, but unfortunately doesn't remember which panels were opened when Firefox is exited/restarted. It also seems to forget any other options changes ...
So for the time being I have to manually re-open all my panels each time I have to restart firefox ...
But at least I can open them ...