Thanks guys 
The item buttons are completly transparent in the center thus following the contur of the panel no matter where they lie.
I want to do the same for the logoff buttons as well, but WB seems to have problems drawing the buttons correctly when in mouseover state. The button image for the mouseover buttons is exactly the same (only the glyphs change color to show state change), but WB doesn't like light shadows on mouseover buttons. The light drop shadow all but dissapears! 
I have seen this before and it's damn annoying!
Any advise on this would be appeciated