You could run litestep on top of Explorer. Not sure the specific settings but if you check the litestep documentation on shellfront (http://lsdocs.shellfront.org) in the 'litestep' section there should be all the info you need (such as command-line arguments, etc).

You can strip it down or make a stripped-down theme so the only module running is VTray, and Explorer is your shell for every other purpose. (I think if you do that though you'll have to find a way to manually stop Explorer from running its default systray)