It's a little inelegant with all the inline stuff, but I'm now preserving a little bit of state in the SelectionTool.  I've also made some fields in the AttributesPanel public so that I don't need to add any code to it in order to modify it.  I can just manipulate it from the SelectionTool, leaving all the logic to it.  Not sure how happy I am with that, but we'll let it ride for now.