Keeping IWC and IW Sized Correctly When Using MAXSIZE

Using Windev and starting to concentrate on the use if internal windows (and other controls). My main window has a SIDEBAR control on the left and an INTERNAL WINDOW CONTROL on the right.

The application windows (INTERNAL WINDOWS) open in the INTERNAL WINDOW CONTROL when called from the SIDEBAR menu or the traditional menu at the top.

My main window opens at maximum size for the screen WINSIZE(MySelf, MaxSize). My question is how do I ensure that the internal window control and the internal windows used in it are sized correctly when the main window is MaxSize or taken back to its original dimensions? I'm not sure how to control the size of the internal window control/internal window.

Any help is appreciated.