Controls overlapping DockPanel are covered

[TeoMan]

My DockPanel does not cover all the main window but leave a space for a bar (Please, I need it like this and I can not change the layout).
If the DockPanel and the controls does not overlap, no error;
otherwise if I design a overlapping area like in this image (Again, I need it like this) (DockPanel is in the upper part but it is "SendToBack" and is overlapped by a panel on the front up to the dashed line)

On run I get this layout:

If I open a DockContent (as MDIDocument) inside the DockPanel I get this annoyng horizzontal line that is drawn by DefaultDockWindow.OnPaint

I am using Vs2017 and latest 3.0.6 nuget version

[lextm]

You might share a complete sample somewhere so that others can investigate what's wrong.

[TeoMan]

WindowsFormsApp1.zip

Start software and see the first issue
Press button1 and see the second issue

Hope this can help

[cuppm]

I just tried your example using 3.1.0 with the 2013 light theme and it looks like I would expect it.