You're dependent on the wood fibers that the screws are biting into to hold everything together. If you replaced the screws with through-bolts and locknuts (say, 1/4" diameter), with fender washers on both sides to distribute the force, you'd be in better shape.

I'd go along with the recco to have heavier metal. That galvanized sheetmetal isn't very stout. You can bend it with your bare hands. Steel bar stock would be a lot sturdier.