Child WinForms in Touch Screen Application in .Net

Task:
I had given a task about showing child windows in Full Screen mode properly
Issue:
What was done before I start to fix this issue. 
An MDI form was created with a menustrip with one menu item in it and setting its 
MdiWindowListItem property
For details: http://msdn.microsoft.com/en-us/library/system.windows.forms.menustrip.mdiwindowlistitem.aspx
Briefly it maintains the childwindows in MDI so it is normally necessary to set in MDI applications.
We had set these properties at MDIWIndow Level:
this.FormBorderStyle = FormBorderStyle.None;
this.ControlBox = false;
this.ShowIcon = false;

this.WindowState = FormWindowState.Maximized;

When we create an instance of  child window we also set these properties of the instance of the form:

ChildForm childwindowfrm = new ChildForm();

childwindowfrm.MdiParent = this;

childwindowfrm.Show();

childwindowfrm.Focus();

We had set these properties at ChildWIndow Level:

this.FormBorderStyle = FormBorderStyle.None;

this.ControlBox = false;

this.ShowIcon = false;

this.WindowState = FormWindowState.Maximized;

After setting all this, we noticed that whenever we open some child there is a flickering and the Title Bar and ControlBox of the child form appear and disappear immediately. Getting Visible and invisible are noticeable on machines like Core 2 Duo with 2 GB RAM, Windows 7. On i3 it can be ignored but if you see then this issue exists on every machine. ControlBox must not appear in any case.

Solution:
ChildForm childwindowfrm = new ChildForm();
// These two bold lines fixed the issue
childwindowfrm.TopLevel= false; 
childwindowfrm.Parent = this;
childwindowfrm.Show();
childwindowfrm.Focus();
Reason:
Menustrip gets the child and make it visible but child sets its properties later. That is why flickering   has not be noticed.