Hmm... I don't think I've ever failed to get something to on top of the one more slot gimzo; even sims. That's using 'move_objects on', of course. Often I add the Magisplay Tray to the mix, though; and then put the tray on top of the One More Slot thingie.
Still, it can't hurt to learn what bits you need to flip to just fix the objects that you want to fix.
Warning: Never save a lot if you have a sim on a Magisplay Tray. If you do, you will not be able to reload the lot.