VS 2010 MDI Child Form Size

My project has a Main form as MDI parent and all other forms are children to Main. I would like all children forms to appear maximized within the parent form. In VB6 all I had to do was set the form's WindowState to Maximized. This is not working in VB2010. All forms appear the same size I see in the design window. What do I need to set? Thank you.