You will need a custom designer, and in the OnSetComponentDefaults override,
do something like:

 MyBase.Control.Dock = ...

Let me know if you need more info on custom designers.  Meantime, a look at
DesignerAttribute should point you the right direction to get going.

Best Regards,

Andy

Hi Brian,

I agree with Andy's suggestion, here goes the code.
<DesignerAttribute(GetType(TestControlDesigner))> _
Public Class UserControl1
   Inherits System.Windows.Forms.UserControl

'........ omit the generated code

End Class

Public Class TestControlDesigner
   Inherits System.Windows.Forms.Design.ControlDesigner
   Public Overrides Sub OnSetComponentDefaults()
       MyBase.Control.Dock = DockStyle.Top
   End Sub
End Class

You may also take a look at the ControlDesigner Class.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/
frlrfsystemwindowsformsdesigncontroldesignerclasstopic.asp

Best regards,

Peter Huang
Microsoft Online Partner Support