Please run the attached sample project.
1. Click the Child Form button.
2. Maximize the MDI child form either by clicking the maximized button or by double-clicking the title bar.
You will notice that there is an empty space between the docked command bar and the top edge of the form.
I have also updated your Telerik points.
Unfortunately, the issue is at a location that is too deep in the RadForm functionality for any customization to have effect on it. We will do our best to introduce a fix accordingly. Please excuse us for the inconvenience caused.
Regards,