Can I mount a sconce directly to a plaster lath wall by screwing the mounting plate to wall? wire feeds thru hole in wall, thru plate, connections made including ground. The sconce is screwed to mounting plate thru ears on plate holding it snug to the wall. Sconce is a 4 1/4" cube with a 10 watt LED light. sconce is 80" above nose of step in stairwell.