Control the container 'area' of a custom container control

I'm working on a user container control that is collapsable and has a caption bar and takes on a similar appearance as a form. Currently at the control's host's designtime, the area to drop controls into the control is the control's bounds. I want to shrink it so the the border that i'm draing and the caption bar are not obscured by or obscuring the nonclient elements of my control. Basically, I want similar functionality to the tab control (I.E. You can't place child controls over the tab strip at the top). How do I do this? What method do I override or what base method do I call from the SizeChanged event?

Hi Were you able to get a solution for this?

the post is 15 years old and the OP didn't post anything since 2011... I have some doubt about getting any answer