I had to mount an Amplifi HD router to the end of a 38 mm handrail so I have designed a custom print in place clamp for it. My version mounts the Amplify HD tray with a tiny ballhead using standard ¼-20" UNC camera nut & bolt. To close the clamp you have to melt a Ruthex M3 heat set insert to one side and lock it with an M3x12 bolt from the other half. Later on I realised the clamp itself might be useful to anybody else so I made the design parametric and uploaded the Fusion 360 CAD file as usual. Enjoy!