Well, I figured this out midstream but I figured I'd post it for anyone else who runs into this behavior. ToolTipText wasn't viable no matter what I tried, but I was able to add a ToolTip control to the main form and hijack that. I set the ContextMenu's ShowItemToolTips to False and handled the display of the ToolTipText text manually.
You can't use a ToolTip control with a ToolStripMenuItem (because the latter isn't a control), however you can use it with a ContextMenuStrip, which is the Parent control of the mnu itms. So, I added Handlers for the MouseEnter and MouseLeave events of each ToolStripMenuItem and used those to display/hide the ToolTipText for each mnu item. This got rid of the pop-under issue for the most part. There are still occasional odd behaviors, but it's a viable solution.
Sub LoadMenus(acct As ToolStripMenuItem)
AddHandler acct.MouseEnter, AddressOf EMToolTipShow
AddHandler acct.MouseLeave, AddressOf EMToolTipHide
End Sub
Private Sub EMToolTipShow(sender As Object, e As EventArgs)
ttpEM.Show(sender.ToolTipText, sender.GetCurrentParent())
End Sub
Private Sub EMToolTipHide(sender As Object, e As EventArgs)
ttpEM.Hide(sender.GetCurrentParent())
End Sub
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…