Well after several hours of trial and error and searching I think I have it. In case someone else needs this, here is what I did.
In your web.sitemap file you would add the attribute for example for the expanded setting
then in your code you would add this:
sender, Telerik.Web.UI.RadPanelBarEventArgs e)
e.Item.Expanded = Boolean.Parse(((System.Web.SiteMapNode)e.Item.DataItem)[
It's just that simple.