New version works for simple cases. Multi-node sets hang on Union. Pretty sure it has to do with last node in Union chain per set not having a Next of null before the final Union in Test08(). Which in turn is being caused by the same thing causing the nodes to chain backwards. i.e. 1U2, 1U3, 1U4 should result in a Next chain of 1->2->3->4->null. Instead it results in 1->4->3->2->1->...etc. Too tired right now to see the problem...