My Atari 400's membrane keyboard was bending, squeaking, and making it (even more) difficult to press the keyboard buttons, so I decided to print a support piece that fits underneath it to reduce the give. It definitely improved the response of my keyboard and got rid of the annoying squeaking noises, so I'm happy with how it came out!

Just open up your Atari's top piece and slide this piece underneath where the keyboard will sit on top of. It helps to position the downward facing lip of the piece on top of the little metal bracket just above the controller/joystick inputs and use that as your primary positioning and brace point.

Enjoy!