I've approached 3D design quite recently, due to our work with VR video.
For this purpose, I designed several iterations of 3D printed mounts for our arrays of GoPros, adapting to different use cases.
The following designs have all been printed with a DaVinci 2.0 Duo, which is cheap and effective.
The only significant weak point is the camera mounting thread, which can easily break with lateral hits, or if the screws are tightened too much.
This one only needs four compatible GoPros. There is quite a bit of overlap between the resulting images, so the cameras can be mounted in portrait mode, obtaining better vertical coverage.
It's a very sturdy system, which requires comparatively little material to build and has a minimum amount of flex. It has been successfully used in a variety of settings, including during live opera recordings at the Regio Theatre in Parma, Italy.
As I found out the hard way, the cameras mounted in this way do not have enough coverage for underwater panoramic videos, due to the different refractive index.
For 3D video and underwater uses, we use 8 GoPro Session cameras arranged in a ring.
It should be compatible with any GoPro, most action cameras in general, and is available here.
The images we obtain are around 5700 pixel wide, but have rather sizeable holes at the top and bottom.