If this entry shows up, I've successfully moved the tomster.org Plone instance into a separate Zope instance. I've got six Plone instances running on this machine meanwhile and it simply wasn't feasible any longer to have them running inside the same Zope instance.

I've also switched to the vanilla install from the Ports collection, rather than my own (meanwhile cumbersome) recipe and I really appreciate the elegance of the new setup.

I probably should write a recipe on it ;-)