I needed a longer projector mount arm to hit the mounting points on my projector. This one should fit into a Monoprice (probably others, too) bracket and has enough reinforcement to be plenty strong.

Printed on its side to improve strength in the direction with the most stress. Ream out the rear hole to fit an M5 screw or nut & bolt depending on what works best for you.

I printed samples in both PLA and ASA with 5 walls and 25% infill, and both were very rigid and durable.