I didn’t like that when xfce4-panel is in a fixed position and not expanded to the full width of the screen, it sets _NET_WM_STRUT and _NET_WM_STRUT_PARTIAL which reserves space at the screen border.
The unused space on my tiny screen above the maximized window annoys me, so i downloaded the source whith apt-get source xfce4-panel and added a setting to disable setting the _NET_WM_STRUT properties.
Here’s a tarball of my patches.
The setting can be enabled by editing ~/.config/xfce/panel/panels.xml and add (or change if it already exists) <property name="disable_struts" value="1"/> in the <properties> element.
A better long term solution would probably to have the window manager ignore struts for maximized windows when a panel does not cover the entire border.


MMN-o