The binding for the resizing is a good idea, since I'm not sure yet what would happen exactly when resizing (manually) between my hide/show actions.

Still, if I'm honest, I think this is a limitation of Tk: imho their should be more automatic resize options than me coding and remembering the size of all frames. For my app this is still doable, but for larger apps this would become very cumbersome!
Well, I probably just have to live with it; maybe someone will make a widget->hide() and widget->restore() to ease doing this. thx for your help !