This small support, easy to print, allows, without having to produce the whole case, to mount devices on top of Raspberry Pi 3B official case.

It offers some resistance to assembly and remains slightly curved like the case lid.

Can be used in other projects thanks to an M5 hole.

I printed it with 50% infill and 0.2 resolution.

I used it to mount an unofficial IR camera with illuminators: mine has 52mm of distance between the center of the illuminators.

OnShape document: https://cad.onshape.com/documents/e95902a6f2ab74ef667acb42/w/23e72145ea66dbd2db7fc3cd/e/2a2f9558edc9d3bb428f8876

Edit 2023.06.30:
Someone asked me to mount an old usb webcam (LogiLink UA0155), so I prepared an adapter (USBCameraMount).

Meanwhile I had already printed a support for a microswitch (ButtonCase) - it can be snapped into the base.