This mod (PrivateMessageGUI) is not anything like I was hoping.  In fact since it uses the in game tagging method and you type a long sentence it looks very odd.

Can you work with @MisterPixie and develop a GUI with tabs for the different PMs that are open with the ability to chat in them and close them.  I think this type of PrivateMessageGUI is better.  I have also posted this at the PrivateMEssages help chat!