Dockstyle and mdichild window

I have a main window which is a MdiParent and to which i add a couple of other windows(on some event) as mdiChild using the show() method. I want each child window to appear at a particular position for which i use DockStyle properties.

But the new window which opens up resizes itself to the height or width of the original window depending on the dockstyle. I want the size of the mdichild form to remain as it is. What property should i set for this.

Also when i change controls among the child windows, the window moves from one place to another, how do i avoid it.

Thanks