Hello! I'm trying to build an application where I have a top banner with a fixed height, and the components below should take the rest of the screen. This works when you start with a template (Jewelry box for example), but when I want to create my own thing, the components don't "snap" to the fixed panel, so as you resize the screen, they start to overlap:

As you can see in the image, below the banner I have a fixed panel (yellow) and a Sidebar. They both overlap the top banner as soon as I start resizing my browser and reducing the height.
Both have "stretch" selected for height configuration. When I try to resize either of them vertically it won't let me "snap" it to the top banner (which is also a fixed panel).
Any thoughts?
Thanks!
Alejandro