Right now, there is no way to completely disable the listing of subforums on the Forum Index page. In vBulletin, we were given a method to only show forums at a certain depth. This is a nice feature for us with a lot of forums. After deleting almost 600 forums on one of my sites, I am still left with almost 400. I don't display subforums on Forum Index currently by the way of a CSS edit. This does not prevent xenForo from rendering all the subforum html though, which still inflates the page size. We really need a way to control this.