This is simply an annoyance.
But the system seems to stack child windows properly for a while, but then at some point, before you expect it to, it begins re-stacking them over the top of the ones you've already laid.  
Are there any configurations I can set?  I mean for the size of the MDI setup that I'm missing.  It seems to stop before the center of the screen.  I will post a picture of a test project, but it is a little similar to what happens in the real project.  I realize that I can do a 'Cascade' and other functions, to windows after they already in place.  But that is not desirable.  I also realize that MDI forms fell out of fashion a while back.  Well... I'm not getting rid of them yet.
                        
I think this is what Hans was saying: In the test project I put this, and it works... Note: This is in the load of the MDIChild.