setHeight on DockLayoutPanel won't shrink the north widget

[M]

I want to shrink the height of DocuLayoutPanel by calling panel.setHeight(String px) however, this call won't shrink the north child of the panel. How can I shrink all the widgets so that overflowed widgets are not visible? With even setHeight("0px") north child remains its full height assigned (which is 58px in below case)

Here is my markup:

    <g:DockLayoutPanel unit="PX">

         <g:north size="58"><g:HTMLPanel>North Child</g:HTMLPanel></g:north>

         <g:center><g:FlexTable /></g:center>

    </g:DockLayoutPanel>

Thanks in advance!