Read again kev, Hiding the taskbar is an option you need to check, the system tray is a tabbed dock, not a regular one. all docks can be removed or altered in almost any way.
I feel like a dumbass lol. Y'z shadow has a "langage" setting, you can turn the language to english, then browse the settings without the aid of a translator. the final tab in settings is "exclude". here there is a magnifying glass you can use to exclude certain windows which you drag and drop. Drag to messenger, press apply and no more dodgy shadow! I have to admit, it was ****in me off too kev
Peace