I have three of the HS300 (US/2.6) but (unexpectedly) these didn't come with any wall-mounting hardware to fit the hole/slots on the back of the unit. What is the recommended hardware type/size? The hole has two slots, but there is a plastic divider at the entrance to the slots which seems to prevent my standard pan-head screws which fit through the hole from sliding along the slot. So what hardware works here for attaching the strip to a wall or under a desk, etc?