I was stuck on this for a little while, so I thought I'd share my solution.  All of the examples using a CFormView to create a Dialog-based docking pane only made use of a single view class.  I make use of the Docking Pane ID to handle each pane's creation:

int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct) {  ...  // Create docking panes.  CXTPDockingPane* pPaneProperties = m_paneManager.CreatePane(   PANEID_FORMVIEW, CRect(0, 0,210, 120), xtpPaneDockLeft);  CXTPDockingPane* pPaneSecond = m_paneManager.CreatePane(   PANEID_SECONDFORM, CRect(0, 0, 210, 120), xtpPaneDockRight);  return 0; }

Then in the OnDockingPaneNotify message handler, you can use a switch statement to conditionally create the appropriate panes:

LRESULT CMainFrame::OnDockingPaneNotify(WPARAM wParam, LPARAM lParam) {  if (wParam == XTP_DPN_SHOWWINDOW)  {   CXTPDockingPane* pPane = (CXTPDockingPane*)lParam;   if (!pPane->IsValid())   {    switch(pPane->GetID())    {    case PANEID_FORMVIEW:     if (m_pFormFrame == NULL)     {      m_pFormFrame = new CFrameWnd;           CCreateContext context;      context.m_pNewViewClass = RUNTIME_CLASS(CSimpleFormView);      context.m_pCurrentDoc = NULL;           m_pFormFrame->Create(NULL, NULL, WS_CHILD|WS_VISIBLE|WS_CLIPCHILDREN|WS_CLIPSIBLINGS, CRect(0, 0, 0, 0), this, NULL, 0, &context);      m_pFormFrame->ModifyStyleEx (WS_EX_CLIENTEDGE, 0);      m_pFormFrame->SendMessageTo Descendants(WM_INITIALUPDATE, 0, 0, TRUE, TRUE);     }     pPane->Attach(m_pFormFrame);     break;    case PANEID_SECONDFORM:     if (m_pSecondFrame == NULL)     {      m_pSecondFrame = new CFrameWnd;      CCreateContext context;      context.m_pNewViewClass = RUNTIME_CLASS(CSecondFormView);      context.m_pCurrentDoc = NULL;           m_pSecondFrame->Create(NULL , NULL, WS_CHILD|WS_VISIBLE|WS_CLIPCHILDREN|WS_CLIPSIBLINGS, CRect(0, 0, 0, 0), this, NULL, 0, &context);      m_pSecondFrame->ModifyStyle Ex(WS_EX_CLIENTEDGE, 0);      m_pSecondFrame->SendMessage ToDescendants(WM_INITIALUPDATE, 0, 0, TRUE, TRUE);     }     pPane->Attach(m_pSecondFrame);     break;    default:     AfxMessageBox("Unknown pane ID");     return FALSE;    }   }     return TRUE; // handled  }  return FALSE; }