NYhifi, not for nuthin, but toggles on metal studs are 110% more reliable than mounting to a piece of plywood the way you said. We had a client that was weary about it until we a co-worker and I hung off each side of a bracket in his house (a total weight of about 400lbs)and it didn't move at all. Toggle bolts are rated WAY higher in both sheer strength and tensile strength than any screws you'll find.