For the structure to hold the foam board, I used 2mm copper rods because they were easy to work with. This can be swapped for anything similar. Then you simply need to add elastic bands on the edges of the board to hold tight your poster during the flight.

I used a few centimeters of double sided tape on the poster itself to make sure it transfers effectively to the surface of the wall. If you have problems, you can use a soft material between the copper wires and the board to softer the impact and even the pressure.

I 3d printed a few parts to make the whole build a bit sturdier but as long as it does the job, duct tape is your best friend. Make sure you get enough flight time to safely land before your lipo batteries are empty. The extra weight really reduces the flight time. In the end, my F550 was able to fly with the extra 700g of payload for about 5min with a 4S 2200mA battery.