How do I setup edit permissions like the yacs forum section?

I see that the yacs forum section allows anon posting new articles (topics) and replying to articles, but doesn't allow anon edit/delete of existing articles.

I have the anonymous_edit option set for my list, which let's anon posters create new topics, but it gives too much permission. But, it also allows anon edit & remove, which I don't want.

Rod www.marklewisworks.com