Well, why having both a forum and a mailing list? With Nabble, the two can be one. Your
http://n2.nabble.com/jace-users-mailing-list-f1495064.html is both a forum and a mailing list. Looks like that is your core stuff and you probably don't need any higher level stuff on top of that.
If you also have a dev list, you may want to create a parent node, and put dev and user under it, like this one:
http://n2.nabble.com/Audacity-f238276.html