Centripro for gopro hero, v4 in my case. This thingy was designed by me cause I could not find such centripro as I want it using with the protective housing swapped to the left side and easy mounting. The middle wall has the hole in case there is no time to get the camera out and the screen is needed. Made a hole for the shutter button, but it is actually not needed. Made two holes in each of the wings for the fishing line, as well as 2 holes at the bottom to bind the gopro to the main line so that the safety cord does not get into the lens. Printed with 20% infill and it was strong enough. You need gopro's bolt and nut. But in my case it holds very nice without nut.
Added handgrip STL, firstly the idea was to make spinning one, but to simplify came with this design. Anyway I recommend to use something like a ring instead.
Added video example, first glitching part is 60 fps and smooth part is 120 fps.