CreateParams() property shows default icon on inherited form

The Task

I manage a big application that is based on a main MDI form. All other forms are children of this MDI form or dialogs of the children. As it is a big application, opening and closing the child windows causes some flickering in the whole application. I was tasked to remove this flickering effect as it looks untidy. My main thought was to make all child windows inherit a "Master" form that would deal with all the commonplace functionality that all forms had to include. From here, I could fix any problems in this one central point which would make managing the application much easier.

The Problem

To resolve the flickering, I found a solution on the web that solves my problem. However, not long ago I found that this also introduced a new problem on the "Master" form where if any form had its "ShowIcon" property to false, the "Master" form would force it to be the default visual studio form icon. I narrowed this down to the anti-flicker solution I found on the web (below).

Private imActive As Boolean = False
Private defaultEX As Integer = -1
Protected Overrides ReadOnly Property CreateParams() As CreateParams
    Get
        Dim cp As CreateParams = MyBase.CreateParams
        If defaultEX = -1 Then
            defaultEX = cp.ExStyle
        End If
        If DesignMode = False and imActive = False Then
            cp.ExStyle = cp.ExStyle Or &H2000000
        Else
            cp.ExStyle = defaultEX
        End If
        Return cp
    End Get
End Property

If I comment this out, it works fine but the flickering is unbearable.

The Question

I would like to know if there is an alternative to the current solution or if there is something I can set within the "cp" variable that would remove the icon?

The Example

I have created a quick application that emulates part of my problem. I could not replicate the flickering as this is down to the application being big. However, in this test project, I have replicated a form that inherits a "Master" form with the above code on. This then disallows the icon to be removed (even in the designer). dropbox.com/s/mg9fyfoshakc69z/TestProject.zip

For this replication, I did not need to include the MDI parent, I have however got an inherited form (MasterForm) and a form that inherits it (Form1). MasterForm has code that overrides the CreateParams property. This effects Form1 in such a way that when the toggle for ShowIcon for the window is set to false, it shows the default VB window icon instead of removing it.

Having run the demo application the only difference I can see is the ImActive flag.

Modifying a similar flag added to your test project set had various results for me, I would recommend changing where this is set until you get the desired result.

Set to false after the form is shown seemed to work best.