The pieces themselves seem sturdy enough, but oh my god are 2/3 screws on each side of the "L" next to impossible to screw in due to the angle you're forced at to get these in. I imagine you'd need a much longer than usual impact bit.
Not only that, but the screws themselves seem to have lopsided threads, where a 'corner' of the shape in phillips is more shallow. Phillips can be bad enough with popping your bit out, but it's like these were DESIGNED for frustration, to pop your bit out under any kind of load going into a (pre-drilled, even) stud, punching a hole into the nearest surface.