I have the following in my settings file, which is still under the MainHUD block, but could probably be moved to the Custom block.
Code:
<Window Name="StartButton" alignment="1" alignment_offset="-240,0" backdrop_mo_o="0" backdrop_n_o="0" foreground_mo_o="1" foreground_n_o="1" frame_mo_o="0" frame_n_o="0" size="36,82" visible="true" window_style="1" />