Not sure if you got this working for you or not, but here's how I'm doing it in my application.
dmMain is my docking manager on frmMain. frmView is a mdichild of frmMain. dmMain takes control of frmView with the new AutoDetectMdiChildForms option.
public frmMain()
{
InitializeComponent();
this.dmMain.DockingStateChanging += new DockingChangingEventHandler(dmMain_DockingStateChanging);