Drywall is not a good support medium and over time I'd worry about toggle bolts and the drywall holding up. Remember I think in decades.
The plywood should be capable of 10 times that weight so in other words, good idea.
Hi All, Have read the forum with interest.
I am about to mount a 60 inch tv on my drywall (3 layers) with metal studs, and will put a sheet of 3/4 plywood on the wall first (to spread the weight accross three studs) then the mount onto the plywood.
My experience with toggle bolts has been ok on another tv, but wondering if I could take another router for this tv - what do you think of using mutliple sheet metal screws ( 3 vertical studs, say 10 screws x three lines) to attach the plywood to the metal studs. the tv is 61.7 pounds.