TreeListBoxItemAdapter.OnDragHover() difficulty casting targetItem to expected model type

Hello,
I am trying to override the TreeListBoxItemAdapter.OnDragHover function so that I can selectively choose whether to auto-expand based on the type of the model

However, unlike the other overridable functions (e.g. OnDrop), I am not having success casting targetItem into the model type I expect.
It seems that in this function, targetItem is an unknown ActiproSoftware.Internal type (TreeNode?) and it is wrapping the model. I am not sure how to get at the model that I need.

   public override TreeItemExpandability OnDragHover(DragEventArgs e, TreeListBox targetControl, object targetItem)
   {
	// this cast fails. targetItem is an unknown type wrapping the TreeNodeModel
       var targetModel = targetItem as TreeNodeModel;
       return base.OnDragHover(e, targetControl, targetItem);
   }

I expected this function to work similar to OnDrop, and I would be able to cast to my expected model type like this:

public override void OnDrop(DragEventArgs e, TreeListBox targetControl, object targetItem, TreeItemDropArea dropArea) {
	var originalEffects = e.Effects;
	e.Effects = DragDropEffects.None;

	// If the drag is over an item and there is item data present...
	var targetModel = targetItem as TreeNodeModel;

I could use some guidance or an example on how to properly override OnDragHover to cast the targetItem to its proper type and get the model within it.
Thank you