[Overdriven]

Your other problem is that you're only using 2 screws to hold the mount, so it can rock side to side throwing off your mesh. I'd use all four on the stock nitro mount to attach your mount.

The only aluminum Lowes and Home Depot sells is either thin flashing or extruded aluminum angle. Some of the thicker (1/4") aluminum angle might work, gotta see how much it flexes.