[xmonad] make a window always on top

Hi, I'm using stalonetray as my tray window, it's a tiny floating window. I set it to be on top layer, and it works well in openbox. Now I'm trying to move to xmonad, and I have made it ignored by managehook. But it is sticky in all workspaces, and ignored by window switching operations. But it can not stay on top of other windows anymore. Is there any way I can do it? Thanks. Best Lars