There is a building site next to my office and want to capture time lapse footages. Building process will take months and I cannot keep my GOPRO in place during this whole period. I have to unmount it on a regular basis. So, I built a window corner adapter to ensure the camera will be 100% at the same place, from shooting session to shooting session.
The frame can be fixed on front using 2 suction cups like for example the ones used for aquarium tubing or on the back using standard GoPro mount
There is also a lid to clip on the back of the frame to prevent the camera from dropping while adjusting the system on the window.
Feel free to comment, print it as it is or create your own variation.
------ Update 15/05/2019 ----
Added Fusion360 source file